Hi, Andrea!
It sounds like you have some great dining plans for your Walt Disney World vacation! I'm glad to hear you have made your Advance Dining Reservations; That is the best way to make the most of your Disney Dining Plan!
It is hard to say what will cost the most, but in general, breakfast is the least expensive, then lunch, then dinner will be the most expensive. If you want to do some research, go to www.allears.net and look through the menus. Prices are listed, and while they are subject to change, it will give you a pretty good idea of the cost of the meals.
You might want to pick a restaurant to pay out of pocket where perhaps you know you won't want dessert, or maybe will just get an appetizer in place of an entree. Buffets, such as Crystal Palace, can get very pricey for dinner, so plan to use a Dining Credit for that. In comparison, lunch at the Plaza Restaurant is pretty reasonable.
Do a little research, or
send me a note with your list of restaurants and I can let you know where to use your credits and when to pay out of pocket. Have a great time dining around Walt Disney World!