Hi, Jacqui, and welcome to the Disney Parks Moms Panel.
What an exciting age to introduce your daughter to the Magic of the Walt Disney World Resort! My daughter was three the first time she visited, and six years later she STILL talks about the memories we made on that first trip.
Watching magical videos together is a wonderful way to introduce her to what she might expect during your visit. On the
Disney Parks planning website, there are videos specially tailored for Walt Disney World Resort that you can watch from your computer or mobile device. There are separate short videos for each of the four main Theme Parks, two Water Parks, and even Disney Springs. You'll also find videos about Walt Disney World Resort hotels, as well as planning videos about Dining and Tickets & Packages, too. I would definitely recommend the "Fun For Little Ones" video--a quick, 3-minute overview of some of the highlights you might experience during your vacation.
In addition, the UK website for Walt Disney World Resort includes
Planning Guides for families with little ones or teenagers with even more tips about
traveling with little Mouseketeers (including information about attractions, shows & experiences, dining and family services (among other tips)).
Hopefully these sites will provide you with some information you can use to help prepare your daughter for her journey to The Most Magical Place on Earth!
Amy
PS: Once you're here, make sure to ask for a complimentary "I'm Celebrating" button from your Walt Disney World Resort hotel concierge or from Guest Services at any of the Theme Parks. Let your little princess wear it every day!!