I understand your dilemma then. I'd say its one of those things where..either you don't play at all or let them play with it...or be a jerk I guess lol. I'd be king of the gamepad though in your situation..I think then there wouldn't be much damage they can do.
I decided just to replace it with the Wii... if they ask me why I'll say I wasn't ready to share it yet because it was really expensive.