You make a few points that are actually the opposite of what I'd suggest. You want to eat as-expensively-as-possible to get your money's worth on the DDP. Burgers and pizza are exactly the wrong way to go. Maybe you mean't signature (2-credit) dining? In that case, I agree that the DDP is a poor choice, but I wouldn't bring an infant into a signature restaurant anyways.
A four year old is almost never worth it because he's charged the same price as a 9-year-old. Likewise, a child age 10-15ish will probably never be worth it because they're paying adult prices.
ETA: I did the dining plan one time on a 10-day trip. It technically ended up being "worth it" from a strictly dollars-and-cents perspective, but we were actively trying to beat the DDP by ordering the most expensive entrees even if that wasn't always what we wanted. I much prefer the flexibility of paying OOP, with no pressure to try and make my meals "worth" some prepaid amount.
I think you and I have done this exact exercise before!
First, I completely agree with your points. More often than not (especially on the DLX plan) it is very hard to break even (normally you'll come in at a slight loss). However, it's not impossible, and doesn't require that you order the most expensive items on the menu.
Lets do some examples (some ahead, some behind) just to get a feel. I'm going to assume DDP only (1 TS, 1 Snack, 1 QS).
A day at MK with lunch at Cosmic Rays and Dinner at Crystal Palace
OOP cost
Cosmic Rays
1/2 Rotisserie Chicken - 10.99
1 BBQ Pork Sandwich - 10.29
1 Kids Chicken Nuggets - 5.99
1 Chocolate Gelato - 3.99
1 Triple Chocolate Cake - 4.19
2 Fountain Drinks - 3.29 x 2 = 6.58
1 Lowfat Milk - 1.99
Total Meal - 44.02 * 6% tax = 46.66
Crystal Palace
2 Adult Buffets - 42 * 2 = 84.00
1 Child Buffet - 20
Total Meal - 104.00 * 6% tax = 110.24
Daily Total - 156.90
Spend requirement for DDP - 139.31
Net Gain/Loss - Saved 17.59
Or, lets try EPCOT, with Lunch at Sunshine Seasons and dinner at a menu restaurant (though I'd do Garden Grill, but lets say Coral Reef
Sunshine Seasons
1 Sesame Crusted Tuna with Asian Vegetable Noodle Salad - 11.49
1 Spicy Fish Tacos - 11.79
1 Kids Macaroni and Cheese - 5.99
1 Apple Caramel Crunch - 3.99
1 Creme Brulee - 3.99
2 Fountain Drinks - 3.29 x 2 - 6.58
1 Simply Orange Orange Juice - 3.99
Meal Total - 47.82 * 6% tax = 50.69
Coral Reef
1 Pan Seared Salmon - 25.99
1 Seared Mahi Mahi - 26.99
1 Kids Grilled Chicken Tenders - 8.99
1 Chocolate Wave - 8.99
1 Bailey's and Jack Daniels Mousse - 7.99
2 Fountain Drinks - 3.29 x 2 - 6.58
1 Lowfat Milk - 1.99
Meal Total - 87.52 * 6% tax = 92.77
Daily Total - 143.46
Spend requirement for DDP - 139.31
Net Gain / Loss - Saved 4.15
So, it's not hard to come out ahead or near break even. And I didnt include kids desserts or the snacks!
However, it is easy to come out cheaper OOP depending on how you wish to eat. For example, getting water instead of fountain drinks or milk/oj. Not buying as many snacks. Not getting desserts, or if at a table service, sharing a dessert or appetizer. You are spending less, dollar for dollar, but you are also getting less, so it isnt apples to apples.
So, it really comes down to personal preference, and a limited amount of fiscal awareness (eg dont use a snack credit for a water or popcorn...save it for more expensive items like ice cream treats) to break even or come out ahead.
