Mother-in-law is impressing her religion on our children

 How long is she staying at your house? If it is only a month or two, I think letting her take him to church would be fine -- it could be something they do together. In a way you would be teaching your son that family members can have different values and beliefs. "Grandma believes in ..., I believe in ... People in families can have different beliefs, and appreciate each others' ideas. However, if she's living with you for the long-term, you probably need to research the church and the Sunday School, and work with her to find one that is more open.

My family made a detour into toxic fundamentalism when I was a child, so I felt very hesitant about religion for my son (now age 10).  Have you thought about a Unitarian Universalist congregation, a form of spirituality that is very accepting of all religions?  The older children there learn about other religions and even go on educational visits to various churches, synagogues, mosques, etc.  I am a Christian and we found a wonderful open-minded congregation that suits us, which was a big relief.  If you take some time to explore spirituality yourself and as a couple, you will find peace of mind as well as confidence in what to tell your child.  For us, being respectful and learning about other religions will always be important as well.  

This is a tough one, isn't it? My husband and I grew up with different religions, but in adulthood have both moved on to being more secular, while my parents have remained extremely religious and his parents aren't religious but would like us to raise the kids with the cultural traditions associated with their religion. Our kids (older than yours, but we started explaining it at a young age) understand, like you said, that religion is just a part of everyday life for their grandparents, and they sit politely through dinnertime prayers at grandma's house and mostly ignore the rest - if anything, I think their over-the-top religiousness has sort of turned the kids off to religion. Our line with the kids has always been that religion is a choice and they need to respect other people's choices but think for themselves. We do celebrate some religious holidays, but in a pretty low-key/secular way. Personally, I wouldn't let my parents take my kids to church because my beef is mostly with organized religion and how it gets misused, but that's just my opinion. The first step might be clarifying what you're comfortable with and what you personally like and dislike about the different religions involved, and then you can decide what to pass on to your kids - there are likely some values, traditions and stories worth sharing, and some things that should be discarded.

I would encourage you to attend the Catholic church as a family at least once (so you can evaluate the church and priest for yourself) since it is such large part of your mother-in-law's life and conversations with your toddler.However, I hope you'll take him to other places of worship as well, and hopefully find somewhere that you and your husband feel comfortable so he has a religious "home". That will give him a religious foundation, even if later he decides to go a different direction (and you can make it clear to him that that is an option). I wouldn't leave a vacuum or just leave it up to your mother-in-law.  If the Catholic church is the only regular religious force in his life, it will be where he goes for the Big Questions and he needs your guidance. Personally, I wouldn't send a child to church or temple alone. 

I have an 18 year old and a 6 year old. Like your family, my husband and I aren't practicing, and thought our kids could decide on what they want to do later. In case of our 18 year old, he ended up being just like us, not believing in anything, which is not an easy and arguably not a good way to live. I am prone to depression, and he's gone through a year long horrific depressive episode in his junior year when his classmate died in a fire. Drugs are rampant at all high schools and even some of the middle schools, and he was exposed to that.  I wish he had religion of any kind to turn to when he was feeling low or in doubt. In fact, my psychiatrist handed me the contact info for his rabbi along with a prescription for an anti depressant when I was going through my low point (I am Jewish by background but never practiced).  I wish I could turn to religion, and most importantly, to a religious community for support, but it's hard for me to start on that since I haven't been raised practicing any type of religion.  

I say let you mom in law take your kids to church. She loves them, and is their grandma.  They'll learn some about it, and maybe meet some good friends while at it.  That won't necessarily turn them Catholic. They can decide if they want to become that later.  In the meantime, they'll be exposed to drugs and drinking that what they are bout to be exposed to here in the East Bay.  Again, I wish my teenage son had something other than his high school friends to rely on when it comes to making choices in that.

My husband and I aren’t religious either and have generally not spoken about religion to our girls, who are 5 and 2. But, as our 5 yr old socializes more, the subject of god, worship, church, etc., has clearly come up. Our position is this - people believe in all kinds of things, some people believe in god, some believe in more than one god, some believe in no god. We’ve told her that it’s not important for her to decide what she believes right now but understand that god is really important to some people and  she might hear people talk about things like god and jesus. we told her about church and temples and praying and if she is interested when she is older we can take her to one. OP didnt say how old her son was but, if he is capable of understanding why his parents have different beliefs than his grandmother, it is definitely worth the explanation and that might help him not be confused. as for letting him go to church, that is a hard NO for me, but everybody is different. indoctrination is a real risk when people dont have the tools to question what they are being told. if he is being taught prayers without context, i would find that worrisome, even if MIL clearly means no harm. she could be laying a foundation that totally undermines your intent on allowing him to choose for himself at a later date. i say all of this as someone who had a deeply religious upbringing and took years to “unbelieve” all of what i taught and learn to think for myself. and im not suggesting abuse or coercion or anything, just tons of indoctrination by my family who genuinely meant no harm - it was simply their belief system. but no one told me that i didnt have to agree, i mean, why would they? but i think there is harm in being taught the tenets and practices of a religion, as a child, but with no overall context of what faith means, a singular framework, and little room for questions. 

I come from a mixed religion family, back in the day when it was a big scandal. Both of my grandmothers would ask me if I was going to Sunday school and there was no way for me to please both of them. But I would go to church with my grandmother when she visited us and when we visited her. I liked it. I liked being with her and making her happy. Her friends were always so nice and so genuinely interested in seeing me and hearing about what I had been up to since my last visit. I have a very clear memory of how good the cookies were afterwards. I'm an atheist but I only have fond memories of being with my grandmother at church. I took my son to an Easter service and sat and thought about my grandmother who I still miss so much.

In my opinion, kids should be able to make up their own minds about religion and exposing them to it isn't a bad thing at all. My son and I have big conversations about God and religion and I always encourage him to keep an open mind while at the same time making sure that he understands the problems that it causes. I try to teach him to think for himself, one of my biggest issues with really religious people is their gullibility and failure to see how they're being manipulated to line someone else's pockets. But a lot of people get a lot of good stuff from religion so I don't want him to think that it's all bad just because his parents aren't into it.

I grew up Buddhist also.  As I understand it, following the Middle Way or Eightfold Path, you can also be Jewish, Muslim, Christian, or another religion.  We took our kids to Buddhist church (my spouse being Christian) until we hit a wall when our older one was in middle school.  And then we stopped.  The only way in which I think you may be mistaken is relying on "should it come their way".  Because the religion that comes their way may be one that is truly objectionable, like some cults that I believe used to recruit around colleges.  I think it is helpful for a kid to have some belief system to hang their understanding of the world around, and that it can be purely secular, but in that case I would try to actively inject that shared experience into their childhoods.  I guess I think you could do worse than go to some mainstream Buddhist church or Protestant or Catholic church for a few years.  But obviously different strokes for different folks.