Well, in order to determine the value for your situation, you'd have to determine what you would eat if you did NOT do the
DDP. So let's crank some #'s.
6 days of breakfasts for 4 people-
let's presume 1 box of cereal, plus gallon of milk, plus orange juice and maybe donuts on 1 day
My best guess would be maybe $25.00 for breakfasts with the above items
Lunches for 4 people-
You pack your lunches but decide to buy drinks there b/c of the weight. Lunch includes 1 large bag of pretzel rods, plus 1 large bag of chips for the week, along with sandwiches, meat, bread, condiments, cheese.
Maybe $50 for the week including a nice selection of what the kids like for meats and breads plus 4 drinks each day at a cost of 2.50 each = 70
TOTAL = $120 lunches
Snacks- I am guessing that you will buy mickey ears once, and probably another type of snack too for the kids, probably more but I'm trying to be frugal here so 2 snack per person = 8 snacks @ 3.00 each.
=$24 snacks
Dinners on site at a table service place is probably gonna run $70 a night with tax and tip for 2 adults, 2 kids, and that is just a "burger place".
x 6 nights = $490 for dinners
GRAND TOTAL = $589
You said the meal plan is gonna run you about $600.
Of course the above #'s are estimates- VERY rough estimates. With the DDP, you CAN have steak dinners, and Counter service lunches in the parks, along with mickey ears as snacks. With the frugal plan, you might be skimping- saying "no" a lot to the kids for things like extra desserts etc.
Granted, the DDP will probably not cover every food expense you have. For instance, I would probably need a drink and a snack each day so my snacks would go to the actual food, but the cost of the drinks each day would go out of pocket.
I think in the end, you might be happier with the DDP, but it really depends on what you like to eat. For us, going on vacation is partially, ok, majorly about eating, EVERYTHING, snacks, huge meals etc.
If your family is ok eating cereal instead of sticky buns, and sandwiches instead of burgers and chocolate cake for lunch from a CS, and burgers for dinner instead of steak and seafood, then the frugal way might work well.
Also, if having things like a slide, a larger room etc are important to you then eating frugal might also make sense.