Hello Timothy,
While your Princess may not remember, I think you're in for a fairy tale vacation!
My biggest piece of advice is to not to change her schedule too much. If you're not keen on returning your room for a midday break, consider finding a quiet spot that's out of the way so she can nap at her normal times. While it sounds crazy on vacation, wake at your "normal" times so your daughter can eat when she's used to it. At this age, it keeps the peace and helps you remain sane!
I used to find that my daughter would enjoy not just the attractions but people watching. When she was very young, she was a bit apprehensive when characters approached. And that's ok! Each character has a Cast Member assigned to him or her so just simply wave to the Cast Member to give them a heads up so the character doesn't end up scaring your Princess.
Undoubtedly, I believe Magic Kingdom is the best Theme Park for little ones. There is something for Guests of all ages at each Park but Magic Kingdom has the most attractions your daughter can ride without restrictions. Because Fantasyland tends to fill up as the day progresses, I would suggest going there when you first arrive at Magic Kingdom. Shorter lines will be best for everyone! It's A Small World, The Many Adventures of Winnie the Pooh, and Dumbo - your daughter will love it. Whether you're at Magic Kingdom or other Theme Parks, so many shows are great for little ones, like Finding Nemo the Musical at Animal Kingdom. And this will give everyone in your party a chance to sit and unwind too.
Don't forget about
Rider Swap as well. While you can take advantage of having other family with you, if there is an attraction you would like to ride, you can take turns waiting with your daughter then
swap with another adult so no one is standing in line twice.
Hope this helps! Enjoy your trip this fall!