Same here, just looking at your schedule I'd think you'd be a candidate for the DDP, but you seem to have done the research.
I do think $4 for snacks is optimistic. When you're walking around you get hungry and thirsty, and those carts are oh-so-conveniently placed. You're going to want Dole Whips
Those are probably $4 each. Soooo good though. Mmm. Also, they sell fresh fruit and veggies, so it's not just junk. When your kids asking for an apple, it's kind of hard to say no (at least it is for me). Bottles of water and cokes are I think $2.50. Anyway, just make sure you allot enough for snacks.
We've done the meal plan before, but we had two kids age 3 and under, so we did lots of buffets, shows, character meals, and the kids were free. My DH, who was in charge of the budget at the time, loved not having a running total of what we were spending in the back of his mind. The last time we went, we didn't do the meal plan, but I was in charge of the budget.