nuzmom, in your calculations did you include the cost of those counter service meals and snacks? If you can feed 5 people two Disney meals/day with Disney snacks added on for $100...
For instance:
Liberty Tree Tavern - late lunch
Adult 1 - Pilgrims Feast ($13.79), ice tea ($2.19)
Adult 2 - Tri Corner Sandwich ($10.70), water
Adult 3 - Pot Roast ($13.79), coffee ($2.19)
Child 1 - Mac and Cheese ($4.99)
Child 2 - Corndog Nugg ($4.99)
1 Pound Cake for dessert ($4.29)
Subtotal: $57.02
Discount: $11.40
Total after discount - $48.59
leave $10.00 tip (which is a pretty fair tip) = $58.59
Pinocchio Haus -
3 Italian Subs w/ chips ($21.27)
2 kids mac & cheese ($7.98)
22 oz coke ($2.09)
Total with tax - $33.38
Total meals - $91.97
that includes 1 dessert at liberty tree and a little left for a couple snacks
I think this is a pretty good example of eating fairly good food and coming in at $100.
Granted that is with breakfast at the room (which we do every day except for 1 Donald's Breakfastosaurus. On that day, we eat dinner after AK closes at the Steak n Shake). We eat breakfast at "home" to save time and to give us a break from the crowds at WDW. Maybe this should be on the "weird and cheap" thread, but that's an example of our meals.
There is a convenience with DDP, but for our family DDE works pretty well. We also tend to have fairly long stays. I think that makes a difference, too. We also don't mind just getting some evening snacks in the park and then hitting McDonald's on our way back "home".
My suggestion would be to take a look at a typical day for your family. Look at the menus and do an estimate of what you'd order. If you take a look at a day or two, you'd probably feel pretty comfortable with whichever decision you make. Then again - I tend to be a "planner".