Dermot:
Although your question was cut off, I'm thinking you may have wanted to ask who you will likely see at
Cinderella's Royal Table restaurant, and therefore, allow you to use your FP+ for other princess meets or attractions.
If you have a breakfast or lunch reservation at CRT, you'll likely see not only Cinderella but also Ariel, Aurora, and Snow White. But keep in mind that Disney always says that characters may vary. At dinner, the Fairy Godmother is featured, and at my last dinner there, so were the mice, but not the princesses.
If the popularity of Anna and Elsa continues into the fall like their appearances so far in the parks, a visit with them will be one of the longest stand-by lines of all four theme parks. I would definitely put the Anna and Elsa Meet & Greet on your list for one of your FP+ selections for Magic Kingdom because, as of this time, they are not being featured in any other park or restaurant.
Wishing y'all a magical vacation!
Whitney