For beginners, unrated or U1000, any chess camp should be helpful in providing great exposure to chess. Although most camps will include other sports activities, such as soccer or swim, kids still spend most of their camp time on chess, which means at least 3 to 5 hours exposure everyday. Because it's not tournament setting, they learn by playing, real playing, having fun and enjoying the time with their new friends. They will get used to play a lot of chess, which is good for them to make further progress in future study and tournaments. Chess is like all other sports, plenty of practice is the requirement for any improvement. The greatest benefit from a chess camp is that kids learn to practice.
For advanced players, you want to look at camps that have rating requirement. You want to have some challenges, even if it's in a camp environment. A chess player always has the appetite for competition. S/he wants to win, in anything, and win in style. So the camp for advanced players should be like an intensive training class. Most times there will be a internal rated tournament on the last day.
Anyway, the first priority for a summer camp is having fun. The second is getting into chess playing mode. And the last is gaining some new chess knowledge. As long as your kids can achieve the first two, your money and his/her time are not wasted.