I would recommend, at the very least, that you get the parents of the kids to sign some sort of release form. Also let them know that they are welcome to drop in and watch at any time, so long as they remain quiet. If they have questions, allow them to e-mail or call you with them. I would also point out that in the fantasy realm God does not exist, that the realm has pretend gods that the CHARACTERS may worship. (The mention of God for any parents that may freak to discover their kid's character is a worshipper of some false, make-believe god.) Make sure that everyone who plays the game understands that the game is a game, not reality. I think that would pretty much cover your butt.