Hi Shelli,
The only restrictions on attractions at Walt Disney World are height restrictions. Some attractions can be too tense for some children while others do just fine so this will be your call as you know your child best. I will list the height restrictions by theme park for you.
Animal Kingdom: Dinosaur (40 inches)- intense ride; Expedition Everest (44 inches)-fast roller coaster with the Yeti; Kali River Rapids (38 inches)-water raft ride for the family; Primeval Whirl (48 inches.)
Epcot: Mission Space (44 inches)-intense simulated space flight attraction, Soarin' (40 inches), Sum of all Thrills (48 inches)-simulated roller coaster that you design, Test Track (40 inches)
Magic Kingdom: Big Thunder Mountain (40 inches), Space Mountain (44 inches)- intense in the dark roller coaster, Splash Mountain (40 inches)- water ride with a big hill at the end, Stitch's Great Escape (40 inches)- in the dark attraction, Tomorrowland Speedway (32 inches to ride to with parent, 54 inches by themselves), the Haunted Mansion- no restrictions but can be scary
Hollywood Studios: Rock N Rollercoaster (48inches)- roller coaster with 3 inversions, Star Tours (40 inches)-Star Wars simulated attraction, Tower of Terror (40 inches) - intense unpredictable elevator drop
Please let me know if I can help you further! There are plenty of attractions for your son to ride on, and I know your vacation will be magical!