Hi!
I would opt for the 1900 Park Fare at the Grand Floridian.
here are my reasons why:
1)its not in a park. so its easy to get to from any park in the world (ie don't have to cut a day short in one area to make dinner res on the birthday date at World Showcase for example)
2) there is lots of choice on the buffet menu, lots of 'fancier' things and a 'fancier ' atmosphere
3) princesses!
4) fairy godmother!
5) something you all should enjoy!
regardless of where u choose, don't forget to call the restaurant ahead of time and order a cake to be delivered to the table after dinner (personalized i believe, and i keep readingthat they aren't costly, in the $15 range i think)
Happy birthday to your daughter!
On our next trip to the world, my daughter will be celebrating her 5th birthday, and we would like to do a character dining experience. She loves all the characters, so we are not picky who we will see. In your experience, which is the BEST character meal to do a birthday at? Thank you! 
