Doom is intense. For like, the 12 seconds it lasts. Seriously, if the wait is longer than 10, 15 minutes, don't bother. Hulk is the most awesome coaster they have, the most fun, but also the most intense. Dueling dragons The Dragon Challenge(renamed for harry potter, I guess?) is really fun, it's one of the feet dangly numbers. The Mummy is just super fun, not even really a coaster, more like a really fast theme ride. You go backwards though and there's fire on the ceiling! Shit's cool.
Of course, I'm not the best gauge on what a 12 year old would like, I was already really in to roller coasters at the point.