Also your "OOP is cheaper" scenarios always show drinking water at all meals. Now some may do this, but I'll hazard a guess that it is unlikely scenario for most.
OP, I'd look at your meal expenses for the entire stay, not on a day by day occasion. Though havoc has but up some reasonable numbers on a day where the DDP or DxDP is more expensive, you really need to look at your vacation as a whole to determine what's the best fit for you. If I calculated DH and I individually, the DDP is probably not be a good choice for me...or even just him. But once we factor in 4 growing kids (one of which is under 3 and not on the DDP, but we'll have to still feed) and a weeks worth of places we want to eat, we are saving $200-300 PER WEEK (we'll be there for 2 weeks). Now I do have some OOP expenses planned for meals not covered on the DDP and the possible need for an extra kids meal for my youngest.
In this case, the calculations all included beverages plus desserts. The DxDP is simply not a value is more than half your meals are going to be QS. The majority of your meals need to be TS to create value on the DxDP.
As to children --- The children's prices are an entirely different equation. For many families, the children's plans can save money, even where the adult plan does not.
For families with multiple children between the ages of 3-9, there can be great value in the meal plans, especially when doing character meals.