Hi Jennifer:
I'm a parent of two boys, ages 5 and 3, who have been traveling to Walt Disney World since they were infants. In my opinion, your daughter is at a perfect age to visit the Magic Kingdom. She will likely enjoy the experience, and you will remember it always, and can capture parts of the trip through pictures and video that you can keep a lifetime. I would love to share some of my family's must-dos for our visit to the Magic Kingdom. Your family may have different tastes, but hopefully these recommendations will be a good start to planning your trip.
While only a portion of the many Magic Kingdom attractions, our family always enjoys it's a small world, Jungle Cruise, Mickey's PhilharMagic, Peter Pan's Flight, The Many Adventures of Winnie the Pooh, Pirate's of the Caribbean, Tomorrowland Transit Authority People Mover, and Monster's, Inc. Laugh Floor. Of course, every family is different, and to have a successful trip, you will have to take your daughter's likes, dislikes, and comfort-level into account.
As you enter the park, pick up a Times Guide for parades and show schedules throughout the day. Also have a look at Disney's in-depth planning page for
traveling to Walt Disney World with younger children.
You also can't go wrong with a character meal at
Cinderella's Royal Table.
My best advice is to relax, follow your daughter's pace, and enjoy.