My kids grew up in the parks and at some point we let the 3 oldest (the little one stayed with me and DH) break from us and go off together while in the same parks we were in. We would meet up frequently and then split apart and never had any issues, Again, there were 3 teens together, they knew the parks like the back of their hand, and always stayed together. You know your kids best. It's a combination of factors to consider.