We just returned with our 2 year old DD. This was her 4th trip, so she's starting to become somewhat demanding about what things she wants to do and see. Hopefully, your DD will let you do the leading.

Anyway, her favorite park was MK. We were there for 5 days and we spent about 1/2 our time there. We had to do everything in Fantasyland at least once (except Snow White- "Mommy, we not go in there . . . mean queen in there"). We did multiple rounds on Small World, Cindy's Carousel, Dumbo, and the Teacups. She also discovered Goofy's Barnstormer this trip. We ended up riding it 5 times. It was her favorite. She also loved the Magic Carpets.
This trip, we left the baby at home and took advantage of the opportunity to travel light. DD is potty trained, so the only thing I took with us was a small ziplock with clean pants and underwear in case of an accident (fortunatley, it never left the stroller pocket). I also took her light jacket for cool mornings and evenings. I personally would recommend travelling as light as possible so you have less to lug around, but I know there are plenty of other moms on this board who would disagree. When we went in October with the baby, we needed a lot more stuff. We took a backpack with diapers, bottles, clean clothes, etc. Keep in mind you'll have to carry your stroller, child, and bags with you on and off the bus. Having a backpack gave us more free hands.
All that said, my biggest piece of advice is to take a break and rest. If your DD is like mine, she's ready to go bright and early. We got moving and took advantage of the quiet mornings in the parks when the lines aren't long. We then took a break every afternoon. DD never took a nap, but we forced her to sit and rest. She generally watched TV in the bed and it really helped keep her happy.
If I can answer any other specific questions, let me know.
Enjoy your trip
Leslie