Tati!
You have chosen two wonderful dining experiences for your little princess! Cinderella's Round Table and Cinderella's Happily Ever After Dinner are two completely different character experiences.
At Cinderella's Royal Table Cinderella greets all her guests in the loby of the castle and poses for pictures and autographs. Once inside the restaurant the princess' waiting to meet you include Snow White, Jasmine, Belle and Princess Aurora.
At Cinderella's Happily Ever After Dinner you will meet Cinderella, Prince Charming, Lady of Tremaine (Cinderella's stepmother) and Anastasia and Grizella.
The only character you will meet twice is Cinderella so when she comes to your table you may want to say something like "it was wonderful seeing you this morning at the castle" and she will understand that she has met your daughter before.
When we celebrated my daughter's 4th birthday we brought down a birthday card for the princess' to sign. My daughter loved it and it made a great souvenir!
When you arrive at the park make sure you visit guest services to pick up a free Birthday pin for your daughter to wear. The princess' will want to know that it is her special day.
Have a magical time and Happy Birthday for your little princess!