All of the food in the MDR is "nice". I wouldn't call all of it fancy, you can get a steak/chicken breast/salmon with a vegetable and rice/potatoes from the menu every night, they are listed as lighter options. That to me is kind of "normal", but it's presented in a "fancier" way so it holds with the atmosphere of the dining room. Most of the rotation meals seem to try to be fancy, but are really dressed up nice food. LOL kind of like the patrons- dressed up nice food for dressed up nice people.
Burgers are always available upstairs near the pool deck.
Your 10/11 year olds can eat off the kids menu or the adult menu. My 10 year old pretty much had salad every night because she doesn't eat meat and thought the wheat pasta was gross. My turned 11 on the cruise pretty much had either the steak or chicken from the lighter menu every night. My 10 year old didn't care that her drink came in the plastic cup with a lid, my 11 year old wanted a regular glass (though last cruise they both wanted regular glasses). One thing to remember is that kids meals typically come out with the adult appetizers, so the kids may end up bored/figidity if they are not used to sitting through a 2 hour meal. Bring a book or something if needed. The second night of this cruise our server told my girls that they were allowed to draw on the table cloths with the crayons since it washed out easy. From night 2-7 the majority of our table was covered in drawings and everyone was happy.