Hi Michele,
Your first trip...How exciting! And with a three-year-old it will be absolutely magical!
My suggestion would be to take your time and drink in all the magic. First, check out
www.disneyworld.com where you can find a list and descriptions of attractions in the Magic Kingdom. Make a list of a few things that you absolutely do not want to miss. I like to loosely plan our day, keeping room for lots of the 'unexpected magic' that will happen along the way.
For our family, some of the 'not to be missed' things would be: a leisurely stroll up Main Street and taking in the wonder of the Cinderella's Castle, the 3 o'clock parade (find a spot along the parade route by 2:30pm), the show in front of the Castle (held multiple times a day, check the 'Times Guide' you will get on your way in to the park), and a few wonderful attractions for the little ones (Dumbo the Flying Elephant, It's a Small World and the Prince Charming Regal Carrousel). Also check the 'Times Guide' for the times and locations to meet her favorite characters.
If your daughter is a morning girl like mine was, I would suggest you hit the Magic Kingdom early, and head back to your resort for a nap or a swim in the heat of the day. When everyone is rested up you can head back to the park for the evening and enjoy the amazing fireworks.
Your second day is a great time to visit some other highlights like the Jungle Cruise, Country Bear Jamboree and Tom Sawyer Island. There is so much to do...if you have any other questions please let me know. Have an enchanting visit!