Hi Pat!
How wonderful that you are taking your grandchildren to Walt Disney World! May is a fantastic time to visit. I would recommend going to the
Epcot International Flower & Garden Festival and Star Wars Weekends at Hollywood Studios if you are Star Wars fans.
Cinderella's Royal Table at the Magic Kingdom is available for breakfast, lunch, and dinner. You will meet Cinderella before going up to eat inside the beautiful castle. Princesses and Princes receive a special gift and many of Cinderella's friends stop at your table for autographs and photos. We have seen Belle, Snow White, and Jasmine there.
The Princess Storybook Dining at Akershus Royal Banquet Hall at Epcot includes many Princesses but usually not Cinderella or Ariel. The food is served family style for breakfast and is served buffet style for lunch and dinner. My girls love eating here.
At the Grand Floridian, 1900 Park Fare hosts character dining with Mary Poppins, Alice in Wonderland, and the Mad Hatter for breakfast. For dinner you will meet Cinderella, Prince Charming, Fairy Godmother, and other friends. Both meals are wonderful.
At this point, Ariel doesn't attend any meals as I think she is still at sea with Prince Eric.
I hope you have a magical vacation with your grandchildren, Pat!