My whole extended family camps several times a year at Pinewood Lodge in Plymouth Ma. It's very kid friendly, with a nice clean lake, boats to rent, fishing, they have a couple of playgrounds, and you can have campfires if it's not a high forest fire warning.
The sites are nice, they have a lot of pine trees and lots of shade. The Lodge has a little general store, and a small diner. The Lodge hold some sort of kid friendly event on most evenings. We don't have a camper, so we rent one of the log cabins when we go. They are small, but are great for long weekends.
We love it there...the only downside that I can think of is they do not allow pets.