Rent a stroller- a city mini. Dont use the park provided ones- uncomfortable for the kids. There are plenty of companies that will deliver to your room. Easy-peasy and worth every penny.
You are going at an extremely hot time of the year- we did the same with a 15 month old. Do not underestimate how much the sun and heat will take out of them. Break the day in half. Go in the early morning and beat the crowds and the heat- go back to the hotel for an afternoon nap and return when the sun is cooler. TTA is from what I hear, a great place to take a nap in air conditioning if you must stay at the park. As far as rides- Dumbo, its a small world, peter pan.
IMPORTANT- you dont realize it now but your trip will be VASTLY different than it was when there were just the two of you. You will be slowed down, you will miss things, you wont hit your favorite rides, and the fireworks you plan on seeing will be curtailed because she is just. wore. out.
But- it will be your most magical trip yet because you will relive every character meeting, every princess sighting, and every WOW moment as if it were the first time. Take this trip slow... and don't be disappointed when you dont get it all done. Take a lot of pictures- that age is excellent for looking back at in an album.