Hi Rachel,
My oldest daughter was four when she first went to the Walt Disney World Resorts. It was such a magical time.
If you are going to tell your daughter about the trip, order the free
planning DVD and watch it together. We did this with our daughters and it really helped us find a few must dos in the park. I would have her pick two things in each park and then do them.
Start in
Epcot and tour World Showcase. Great shows, movies and activities at each country that will engage your daughter. Similarly, there are fun activities in the Living Seas, the Land and Journey Into Imagination.
Disney's Hollywood Studios has Toy Story Mania!, Disney Junior - Live on Stage! and tons of other rides and shows. It is a great park to visit the day after Epcot or Animal Kingdom because it is small and with the shows you can rest.
Disney's Animal Kingdom takes you up close with the animals. Kilimanjaro Safaris is an awesome experience. Plus there is the Festival of the Lion King, Finding Nemo - the Musical and the Boneyard.
No trip to the Walt Disney World Resorts would be complete without a trip to the
Magic Kingdom to see Peter Pan's Flight, Jungle Cruise and of course New Fantasyland!
Finally, no matter what you decide, this is my best tip-keep to your daughter's schedule and enjoy all the pixie dust that happens on the trip!
Have a magical vacation!
Beth