Ours simply suggests that over 6 year old use the appropriate change rooms, I don't have a seven year old yet but I am hoping that by that age I would feel they are able to dress themselves ok after swimming - if the child didn't feel comfortable then would use the family change rooms but if the child is happy to get themselves changed then I would be happy (boy or girl going into change rooms on their own - e.g. girl in womens if taken swimming by DH). My biggest worry would be the child taking forever by themselves.