Hi Sarah,
Thanksgiving is a wonderful time to visit Walt Disney World. You will get to see some of the Christmas decorations up in the theme parks and resorts! It looks truly magical. I would recommend making Advanced Dining Reservations as this can be done 180 days prior to your vacation.
There are two restaurants that allow you to see many princesses.
Princess Storybook Dining at Akershus Royal Banquet hall in Epcot at the Norway Pavillion is a wonderful buffet for breakfast, lunch, or dinner. You usually see Belle, Jasmine, Snow White, and Aurora. It is one Table Service meal on the Dining Plan.
Cinderella's Royal Table at the Magic Kingdom allows you to eat in the Cinderella's Castle. You are greeted by Cinderella and have a photograph with her which you will get to keep. Throughout your meal, other Princesses such as Belle, Snow White, and Aurora will come by your table as well. It is two Table Service Meals on the Dining Plan. My family has been to both of these restaurants, and they actually prefer going to the Princess Storybook Dining at Akershus Royal Banquet.
Please send me a follow up question if I can help you further. Have a magcial vacation, Sarah!