Hi Amanda, what a special day this will be for you and your daughter...so many memories. Make sure you bring a camera and have cast members (and other guests) take pictures for you. As far as what park, you really have a lot of options. I would probably head back to Magic Kingdom as I have so many awesome memories there with my children but there are also some great attractions at the other parks.
Hollywood Studios has many attractions you can share with your daughter. You can have fun in "Honey, I Shrunk the Kids" play area, Disney Junior - Live on Stage!, Muppets and the Voyage of Little Mermaid.
It would also be fun to bring her to
Epcot to experience The Seas with Nemo and Friends and Turtle Talk with Crush. I actually came across a video this week in my Mickey Moms Club newsletter titled "Little Timmy Goes to Epcot" - it is a cute video and you might enjoy watching it. You can find it
here.
I hope this gives you some ideas. Have a wonderful time! Diane