Pizza - they will deliver to your disney hotel and you can eat the leftovers for breakfast
Buffets - Trails End at Fort Wilderness is 16.99/adult for diner and Corando springs or Yaght club breakfast buffet with seatings as late as 11am for 15.99/adult
If you want to try a seat down diner - do a late lunch - most serve until 3pm, this will save you a few bucks/meal. Or ESPN isn't too bad price wise and our boys teenage boys always enjoy eating here each time we go.
Eat breakfast in your room even if your not in a villa that has a kitchen you can still bring a toaster for bagels, juice, milk, cereal etc...
buy a case of bottled water and have everyone bring one to the parks each morning (this will save you at least $2.00/person/day) Extra snacks, soda
I Never cook on vacation anymore (my vaca too) but this is a quick meal to do so If you do have the kitchen make grinders one nite and then go out for sundaes instead of a meal
You dont say how old the teens are (other than the 11 year old) but if they are into the arcades then assign them chores NOW, which they earn a few bucks each week for. Get a white envelop with each childs name on it, the money they earn each week goes into their envelop. When you go, thats the money they have to spend - no more then what they have earned! If they spend it on arcade games fine, on toys thats fine too or even on candy or that second snack at the park as long as you make it perfectly clear that they will get NO money from you, what they get at the start of the trip is all they are going to get so spend it wisely. This always made my kids alittle bit more aware of how much money they were spending and usually took more care in purchasing that special something to bring home. Dishing out a buck here or two bucks there for 6 teens everytime you turn around will really add up quickly