Addressing it from that perspective is even simpler. If a child, who had not received permission from his parents to go there, chose to trespass on private property for the purpose of playing peeping tom, it is the child who has broken the law, NOT the people of the camp. It is no different from that same child walking onto your property, hiding in the dark, and trying to catch a glimpse of you or your spouse naked. It is the kid who has broken the law. The point being made concerns the teens being welcomed by the people at the camp -- the campfire nudists knowing the teen is there and not sending him or her home.
This type of irresponsibility is not necessarily grounds for a criminal prosecution. It is or should be grounds for revoking the land-use permit.
If the campers see the kid and call the police that's a different story.