I have two dds (8,6) and they always love the princess dining. Akershus at Epcot and Cinderella's castle at MK. In my opinion, most of the character breakfasts are comparable with quality and price, but the best two character breakfasts are Cape May at Beach Club and Ohana at Poly. Garden Grill is a nice, family style dinner served at Epcot. Also, will you be using one of the dining plans? Some love them and are convinced they save money. Others don't think so highly of them.
My advice is to not try and do everything. It has been 10 trips for us, and we still have not done everything. As such, select your dining choices by your location and theme park day. Disney transportation is great; however, you don't want to spend hours each day transporting to different locations. Thus, if I am in MK, then I don't want to walk to exit the park, get on a bus, go to another resort or park to eat, and then transport back. When in MK, eat in MK. Also, plan a day during the middle of your stay to spend time at the resort. That way, the children can swim in the pool, play games (there are lots of activities), and the parents can rest and recharge a bit.