We found that doing a late b'fast or late lunch at a character meal buffet would overlap and serve as two meals. While character meals aren't cheap, you have to consider the time they save because you aren't standing in all those lines, waiting for autographs and photos with the characters. This falls into the "time=money" equation for Disney. Of course, this works at regular ts restaurants, too... just choose meal times carefully.
Seriously, portions are huge at WDW. DD and I shared many cs meals on our last trip. Breakfast platters at POP have a significant amount of food; DD and I routinely shared them. Adults can get a kids meal at cs locations, or two kids can share an adult meal. 50's Prime Time has reasonably priced options (and some more expensive) for ts. Starlight Rays has a chicken and ribs combo meal that would feed two adults and two kids (OK, maybe you'll need a side with that at supper, but still...). On the bright side, we found the chocolate cake and carrot cake desserts at the cs locations to be gross, so you can save some money there! In fact, I'd never order dessert with meals; save the money for an amazing snack later in the day!
Doing just cs is your cheapest option, but it won't limit your dining. CS in Morocco and Japan are wonderful places to eat. Breakfast in your room is also an option. Are you driving to WDW? Is your CM contact there? Have them get you some cereal, bagels, cream cheese, milk, juice pouches, and a styrofoam cooler (if you are staying at a value). You can replenish the ice in the cooler each evening... yes, the milk will stay fresh. If you are worried, buy milk by the quart in your food court. It'll cost more, but not as much as buying breakfast every day. You could even have bread, pb, and jelly in the room and bring sandwiches to the parks for lunch, if you really needed to save money.
I won't kid you... food isn't cheap at Disney, but you CAN survive eating just from the cs locations and not eat burgers, dogs, and nuggets your whole trip. In fact, you could eat strictly cs for a week and NEVER eat a single burger, dog, or nugget. Just think about what's being offered for food and how to best plan meals (sharing, etc) to keep everyone happy.