Hi Heather:
I have two boys, 5 and 4, who have been traveling to Walt Disney World since they were infants and who love Animal Kingdom. When we visit that park, we always hit Kilimanjaro Safari, a ride through the 100-acre park savannah where we typically see rhinos, lions, giraffes, flamingos, and many other animals along the way. You know your kids the best, but many younger Guests enjoy this attraction. The animals are tame and generally quiet, and you are seated the entire time so there is little on this attraction that I imagine would bother a child.
We also hop aboard the Wildlife Express Train and visit Rafiki's Planet Watch area, Affection Section, and Conservation Station. My boys also spend a lot of time playing in The Boneyard, a dinosaur-themed playground. The Boneyard features a multi-level maze, climbing areas, tunnels, and a large shaded sandbox where kids can dig up fossils. TriceraTop Spin is also fun.
If you have time, there are also a number of
shows to enjoy, such as Festival of the Lion King, Finding Nemo - The Musical, and Flights of Wonder. When you get to the Park, remember to pick up of Times Guide to find times of various shows and events.
I would avoid Dinosaur, a very loud, dark and scary attraction. Also, my boys (and me, cough), think It's Tough to be a Bug gets too intense.
Enjoy your vacation.