Summer Camps for 6 & 8 YO without the filler

I know I'm way too early to really ask about summer camps for 2020 but we had a pretty uneven to poor experience this year so I thought I'd try to put some better thought into this. Based on the feedback I got from my two boys, ages 6 and 8, I think they really were turned off by the camps that had a lot of transition and waiting time. So for example, one camp I thought they would love, had lots of different sports to try, typically switching every 45 minutes or so. But they said that a large portion of the day was spent transitioning from activity to activity. Even worse was that many (all?) of the activities, the kids had to wait in line to actually do anything. I happened to see their basketball segment and it consisted of two lines of kids, waiting to take a free throw. Super lame. My guess is that they actually spent 10% of their time participating in the actual activity. But I do see the value of the camp because it runs all day and was pretty affordable, so it's like childcare with structured activities. But this is probably the opposite of what I'm looking for, except the affordable part. Now on the other hand, the camp they loved wasn't a camp at all. It was a carpentry class that was a couple of hours each day. Each kid got to work on their own project at their own pace the entire time. Almost zero wasted time. After a snack I'd take them to a park and they could play on their own. So I think I'm looking for:

- Not crazy expensive

- Staffed by a topic expert able to deal with kids

- One to two hours of high quality experience or instruction, no filler (don't need it to be childcare)

- Minimal transitions, minimal waiting

- Preference for sports and outdoors

- In or near Oakland, Berkeley, Alameda