Disney doesn't usually hold back on stuff that could scare kids and I appreciate that. You want really scary? Show them Bambi and tell them that someday their mommy is going to die, too. Show them Up and tell them that someday they will get old and lose the people they love most. Take them on Dinosaur (Actually, don't. If they can't take ITTBAB they sure as heck can't handle Dinosaur!) and tell them how a giant asteroid like the one that killed all the dinosaurs could strike Earth without warning at any point and kill us all.
That being said, if your kid is sensitive to the dark or loud noises, read the dang signs.