First, be VERY happy your kids want to do stuff other than play on their electronics!
My comments are right in line with toedtoes excellent suggestions.
Camping is about the entire family. While we had only one child, what we and other friends did was prior to each trip was to find out what activities were available in the area, that is in the park, and everything within an hours drive. Then put it all in front of the entire family and let everyone pick something. Do one "big" thing each day, like a bike hike, or a hike in the woods, an amusement park, or what ever. Build in smaller things like going with the kids to the park, or swimming. And yes, make sure to take the kids on a few adult things like a winery tour or historical sites. No need to have to make things like that "teaching" times, just let them absorb it on their own. They will say they hate it but the reality is that by the time they are teens they will develop an interest in stuff like that. Play board games and cards together at the picnic table at night. Build in some down time too. In other words, mix it up, make sure everyone gets something out of the trip.
Regarding letting the kids out of site, well that's your call, your comfort level. People can talk about letting them develop independence but we live in a different world than most of us grew up in. How we let them develop independence today has to be handled differently than 40 years ago. I will say that most CGs are very safe places. Again, you as parents have to make that call for your own family. If you do chose to let them on their own, set boundaries, where they can go and how long. The talkies are a great idea, make them check in once an hour, something like that.
And yes, you will be run ragged. That's what having kids is all about. When they leave home, that's when you get to relax and take it easy. Until then, it's non-stop.
All I'll say about the sidewalk chalk is that I hope I don't get so intolerant of kids as I get older that just seeing them have fun becomes that annoying. In other words, I don't ever want to forget what it's like to be a kid, or to raise kids.