How old is nudity acceptable?

There is a communal pool in my city where I go often on weekends. Once a young woman (about25) came in with two boys, about 4 and 11, and no one said any thing, though most people saw them. At one point, me, him, and another girl(all about the same age) were sitting in the hot tub togeather talking. She asked if she could touch his penls, and he said sure. I asked if I could too, and he said sure again! So we both reached over under the water and felt him. It was one of the most amazing things I've ever felt. When it was time for him to go, the two of us girls with him and his familly went into the girls locker room. We all got naked to take a shower, and no one else was bothered by having to shower nude with a naked guy standing there too. Then we all got dressed and went our seperate ways.