Hi Gretchen,
My boys have been traveling to the Disney World parks since they were four months old, & we have always been able to find plenty for them to enjoy at each park. However, the best park for any young child, and my personal favorite is Magic Kingdom.
The Magic Kingdom offers the largest number of attractions and shows which are friendly to guests of all ages and most can be enjoyed without any age or height restrictions. Your daughter will most likely recognize a number of the characters and attractions based on Disney classics, like The Many Adventures of Winnie the Pooh and Peter Pan's Flight. Magic Kingdom is also home to Mickey's Toontown, where you can visit Mickey and Minnie as well as peek into their homes. You will also find the new Pixie Hollow area where you can visit with Tink and her fairy friends. Your daughter will love the sight of the Wishes evening fireworks, as they cascade over Cinderella Castle, and if you have a seat near the Castle, you will also be able to see Tink in flight.
Another great park for young children is Hollywood Studios. The Little Mermaid and Beauty and the Beast live stage shows are beautiful and just the thing for your little princess. You can also find the adorable Muppets in 3D and be sure to visit the Playhouse Disney stage show for some fun with your Playhouse Disney pals.
While Epcot and Animal Kingdom also offer some great activities and attractions for younger children, I would choose the other two parks first for the most magical memories. You can find some great information on traveling with young children at
www.allears.net under the Planning topic and then Infant and Toddle FAQ on the left column.
Enjoy!