Hey Chris!
I love hearing about children who are surprised with Disney vacations!
With respect to getting a call from Mickey Mouse, I know about a service that might be able to help. It's called
Disney Enchanted Calls and it allows you to choose the character, the type of greeting, and the day/time/number to call. While they don't have an option that specifically mentions Walt Disney World, they do have one for a "special trip."
Just for fun, I thought I'd throw out two other ideas that might be worth considering:
Idea #1 - A Surprise Suitcase
If you go to DisneyStore.com, you'll find a wide variety of suitcases that might be fun for her to see propped next to her bed (and packed) when she wakes up that morning.
Idea #2 - A Surprise Souvenir
DisneyStore.com also has a wide selection of Walt Disney World merchandise. It might be fun for your daughter to wake up and find a brand new Walt Disney World t-shirt laid out for her to wear.
Here's a bonus idea from your buddy Derek:
My wife just got tickets for my daughter to see her favorite characters from a children's book series on stage. While this made her super excited...she really got amped up when she got a letter in the mail from the characters. It looked like a page from one of their books and they had a message for my daughter saying how excited they were to have her come to the show.
(Thanks to Daddy's color printer, his light table made for tracing artwork, and an envelope that was stamped and mailed to my daughter from the neighborhood post office.)
Maybe you can help Mickey Mouse write a similar letter to your daughter?
I hope that helps!
Best regards,
Derek