Judy:
What a memory you're making for your granddaughter!
If Ariel is your granddaughter's favorite, I would suggest that you make reservations for Akershus at Epcot and its Princess Storybook Dining! This restaurant also features Belle, Cinderella, Sleeping Beauty, Jasmine, and Snow White, and I think it would be a good choice if you're looking for the most princess characters.
Although Ariel's not guaranteed to be there, she will definitely
not be at Cinderella Castle. (And I hate to mention it, but those reservations for breakfast at Cinderella Castle sell out pretty quickly...)
When you call Disney Dining at 407-939-3643, be prepared to give them your credit card. The Princess Storybook Dining is one of the dining experiences that require a guaranteed reservation!
Wishing you two a magical celebration!
Whitney
p.s. Make sure you register your granddaughter for her birthday if it lands during her stay! Just click
here!