As much as I love Citadels I've had younger players zone out on me during that game, so I think it really depends on what your kids are into. Chaos Marauders might be good if they're in the right age group. Maybe Aye Dark Overlord? Cave Troll is one of the smaller boardgames once it's all out on the table, so that might work. My all-time favourite mass-appeal FFG game has got to be Ingenious, and while that might be light on the components compared to a monster like World of Warcraft, you might think it a little too fussy for camping. Too bad the new Ingenious Challenges hasn't come out yet, that might have fit the bill.
If you look any of these up on Boardgamegeek.com, they ought to have photos of the game in progress so you can judge whether or not it would work on your trip. Let us know what you decide to take!