I think its a pretty strait-forward thing here. . . Use your best judgment. I talk differently in the presence of my nephews as I do, say... around their parents? The same applies anywhere.
When Nova and the kids are in channel, I try my best to watch my mouth. Simply, if I think you're post-pubescent, I'm going to talk about anything I feel like talking about until Ron and the powers that be tell me to do other-wise. i.e. poop, genitals, sex, and the rest of my conversational repertoire of which are not even close to maturity level of decapitation and killing people with guns.
just my $0.02
An 18+ channel would only further their feelings of segregation/isolation. That's messed up, you may as well just kick them out. Maybe just some sort of marker on their name so we know? That would be useful. .