To try to categorize for you:
Roller coasters:
Magic Kingdom: Space Mountain, Big Thunder Mountain, Goofy's Barnstormer (although even toddlers can ride this one).
Animal Kingdom: Expedition Everest
Disney MGM: Rock-N-Roller Coaster
Other thrill rides: Magic Kingdom: Splash Mountain
Animal Kindom: Dinosaur
Disney MGM: Tower of Terror
Epcot: Mission: Space, Test Track
This is just off the top of my head, but I think that's most of the real scary ones. Most of the "scary" rides have warnings on them -- they will warn pregnant women, people with heart conditions, and they will have a minimum height requirement. Some rides aren't really "scary" in the same way a roller coaster is -- like "Star Tours" in my opinion, but that ride does jerk around a lot. I think you should ask a Disney employee (Cast Member) outside each ride you think might be too much for you and he/she will explain the ride to you so you can decide if you want to try it. I find that the vast majority of rides are not "thrill" ones, and like others have said, even the roller coasters at Disney are more tame than many other theme parks. You can go to Disneyworld.com and look at each park. They categorize rides as "Big Thrills," or "Mild but Wild," etc. That might also help you decide what you want to ride. I hope that you have a magical time!
-Dorothy (LadyZolt)