Wrt kids, YMMV. My mom always talked about how my 2-year-old brother had to be dragged onto It's a Small World (at the World's Fair), but I don't consider that a scary attraction. On the flip side, plenty of first graders seem to take Stitch's Great Escape in stride--but a hell of a lot more kids freak out there than, say, Pooh's Hunny Hunt.
I guess we're past spoilers, so the queue features an incredibly life-like witch doctor who dims the lights, a ton of skulls, some decaying bodies, a worm-thing that tries to attack you, and at least one scare-actor. A decent percentage of children are going to have the snot scared out of them by this--particularly because there is no ride vehicle to create an illusion of safety. And a I fear a lot of commando parents ("you know how much we paid for these tickets?!?") are going to ignore friendly warnings and force their kids on anyway.