Hi Misty,
Thanks for visiting the Disney Parks Moms Panel with your question. I believe that the choice for which Disney theme parks to visit is unique to each family. The Disney theme park that you and your girls will enjoy the most will depend on their (and your!) interests. Let me tell you a bit about what I think makes each of the parks that you are considering unique.
Disney's Animal Kingdom Theme Park is far more than a zoo. In fact, one early campaign for the park emphasized that it is "Nahtazu!" which, said phonetically, is "not a zoo!" From amazing experiences seeing exotic animals on Kilimanjaro Safaris, the Maharajah Jungle Trek, and Pangani Forest Exploration Trail, to fantastic Broadway-style entertainment at Finding Nemo - The Musical and Festival of the Lion King, there is so much to do at this theme park.
If you and your girls are more into thrills and the movies, then
Disney's Hollywood Studios might be more your speed. There are thrilling rides here including Rock 'n' Roller Coaster Starring Aerosmith and The Twilight Zone Tower of Terror. These both do have height requirements that you will need to be sure that your littlest one makes. The whole family can ride and enjoy Toy Story Midway Mania! and see the amazing Fantasmic! light up the night.
I suggest that you order the
free Walt Disney World planning DVD. This includes information on Walt Disney World including the theme parks. Your family can watch and decide together which theme park is the right choice for you.
I hope that these thoughts are helpful for you, Misty. Have a wonderful time planning your vacation, and please do not hesitate to ask if you have any further questions.