Hi Kristin,
For the
Dreams Come True Dinner in Cinderella Castle, you interact with Cinderella for pictures before going upstairs which is hosted by the Fairy Godmother. You'll have much more interaction with Disney's royal elite if you do the
Once Upon a Time Breakfast or
Fairytale Lunch in the Castle. I haven't done the Once Upon a Time Breakfast in a while, but I can say there was a lot of interaction the last time I did the Fairytale lunch. The exact characters vary and are subject to change but typically include some of the following: Cinderella, Fairy Godmother, Belle, Snow White, Aurora, Jasmine, and Prince Charming. Every time I've been fortunate enough to be in there for lunch, I've seen Cinderella and Aurora. I highly recommend the Fairytale Lunch if you want to have a meal in Cinderella Castle. No doubt It's expensive, but it can be the highlight of a little girl's trip.
Princess Storybook Dining at Akershus Royal Banquet Hall in Epcot is a great place to interact with the Disney Princesses. Finally, another option is
The Cinderella's Happily Ever After Dinner at 1900 Park Fare in the Grand Floridian. It is typically hosted by Cinderella, Prince Charming, Lady Tremaine, and Anastasia and Drisella. The interactions here can take surprising turns and is a lot of fun!
Have a magical vacation!