Hi Janette,
Have you looked at dining at
1900 Park Fare for dinner? This restaurant has Cinderella, Prince Charming, Lady Tremaine, Drucella and Anastasia dining among the guests. This meal is so much fun and delicious, I would book it just for myself.
It also is a buffet which means your older daughter could eat from the "children's" menu if she wanted too. I sometimes just want a piece of pizza or chicken tender myself. Plus the other benefit of a buffet is you can try new items and old favorites without going hungry.
As for paying for an adult meal and receiving a child's, there is no guarantee this will be allowed. You will need to ask your server what options you have. For breakfast at both
Cinderella's Royal Table and
Akershus, there are non-egg options which your daughter may enjoy such as french toast. You can ask for additional portions for your daughter.
Hope you have a magical time!
Beth