Kid over-sharing/giving money to friends

Curious if anyone dealing with situation of having a child who is a bit too willing to share/give his allowance money to friends? One of our kids is very kind and sweet and I'm starting to worry about him being taken advantage of.  He has a decent allowance since it is intended to cover all of the purchases for him that are not necessities, though he does not buy/want a lot, and we found out a year ago that when he took some money to school/playdates/outings, he would often use it for his friends or give/share with friends.  I knew about him buying snacks to share with his close friends and was totally ok with it, but found out that it expanded to kids he was only casually friends with asking him to buy him stuff from vending machine when they were hanging out in the library, etc.  We addressed it by limiting his cash-spending money and told him the bulk of his allowance goes into his bank account but he can use it to buy anything he wants when in stores with us/or on amazon/online and we will just pay with our credit card and take the funds out of his account.  So we are not limiting his spending (it is still his choice whether to save or spend and on what), but limiting the amount of cash he has on him.   Then shelter-in-place happened and the issue went away since he is home all the time.  His school is likely to re-open in Jan and now that he is a year older we are thinking whether to give him back his allowance without restrictions (since we want him to learn to manage money) or keep limiting his cash (so it is his decision whether to save and spend and on what, but he is not allowed to have more than $5 cash on him unless he needs it for something in advance, like to buy books during school book fair).  I don't mind him sharing or buying his friends things if he wants to (it is after all his money and was intended for him to be in charge of), but I'm worried that he is being taken advantage of and by letting him have cash at this age I'm setting him up as a target.  His personality is such that he still sees only the positive in people, just wants to share/make everyone happy, and is pretty naive for his age (his younger sister is better at reading people and their true motives than he is, and she is the main reason we knew to ask the questions we did to learn about the issue last year).  I don't want him hurt when he realizes that some of his "friends" are just using him, but also don't know how to explain it to him so he understands and can make more informed decisions.  The no cash rules seems like an easy out for us, but I'm worried I'm just postponing the inevitable and taking away a learning opportunity when the stakes are lower. I wonder if it is just my kid or if others dealt with it too.