

No, I would not want to join such an instance but I wouldn’t mind its existence. Nobody could really federate with it. So you create a niche server in an already niche environment.
I am not convinced the conclusion “if the government runs it, the first amendment has to apply” is apt. Even if the server was run from under the house majority leader’s desk - which I don’t think it would, this smells more like an outsourced undertaking - moderation on the platform is not “making a law.” And proprietors of platforms are legally compelled to moderate in certain cases, e.g. when illegal stuff like child sexual abuse is involved.
In summary: you have the cooperation of the parents, you cannot exclude the existence of a mental issues, and you are allowed to spray the item then. These are conditions I put ahead of any other suggestion.