Hello Ylsa!
I asked my 3-year-old daughter and my 5-year-old daughter which park was their favorite, and they both yelled, "Magic Kingdom!" So, when I asked what their 2nd favorite was, one chose Disney's Hollywood Studios and the other chose Disney's Animal Kingdom.
My 3-year old loves music, dancing, and shows, so
Beauty and the Beast-Live on Stage is one of her favorite performances! She also loves
Disney Junior-Live on Stage and being able to meet Sofia the First outside of the theater is a dream come true!
My 5-year-old loves Disney's Animal Kingdom, because, well, she loves animals! Being able to ride in a jeep amongst the animals in
Kilimanjaro Safaris makes her feel like she's on a real safari adventure! She could also spend hours playing at
The Boneyard dig site looking for fossils and crossing rope bridges.
I would recommend choosing the theme park that best matches your daughter's interests. The same advice applies in planning your day at the Magic Kingdom. I recommend arriving before the park opens in order to stay ahead of the majority of the crowds. The first few hours after park opening are wonderful for accomplishing the must dos on your list! You can also visit a website such as touringplans.com which recommends a touring plan for each of the theme parks at Walt Disney World.
If I can be of more assistance, please ask away! I wish you a magical, fantastical vacation with your little princess!
Tania