Oh, that's a tough one. I guess I would have it as a full meeting so as not to single out the boy and his family. It's unfortunate that you have to do it at all, but probably better to make it a "TROOP" rule than just a 'that boy' rule. You may want to mention to everyone that their boys act differently when their parents are not there. Perhaps there is another room they can go to, the library down the street(?) or plan an errand around the meeting so that they aren't there during it. Part of the scouting experience should be getting away from your parents, too (We have families that treated it as low-cost babysitting, so I've been on both sides as well). Good luck!