This may get me flamed, but here goes:
If I recall correctly, you can buy the dining plan when staying on the campgrounds (putting on my flamesuit...). A site is $42 and you can add up to to 10 people to the plan which someone has quoted the price per adult and child ($38 and $12, maybe?).
I realize you are staying offsite, but it might be worth looking into to pitch a small tent (or just park your car!) in order to buy the dining plan, and oh by the way, parking would be free at the parks for you since you're staying "on property", so your net daily cost is now $28/day.
Do this for a portion of your stay (say 2-3 days) and schedule all your character meals on those days. In fact, if you have some ppl who won't be interested, don't put them on the reservation list for the campsite and save even more money by not buying the dining plan for everyone in your group.
Ok, I know I'm a huge bulls-eye for the campground people, but there it is.