Just played with some stuff online......
WDW All Star Music resort from 8/25-8/31 (checking out 9/1) w/5 day non-hoppers=1491.38 if you book through Disney w/no discounts. For the length of your tickets, you'd probably need to get the tickets through Disney if you want to even be eligible for the
free dining.
Room only onsite: 82-141 per night depending upon which nights and what hotel for the value levels.
AAA might make it cheaper, but you can't use AAA rate and be eligible for free dining, if it comes out. You can use AAA as a discount at various restaurants, and shopping though, too.
For me, I'd rather do less days and stay onsite. I'd also pick up the dining, as for the ages of your grand-daughters, it allows some really great dining options that they would probably really enjoy.
We're 5, so staying onsite isn't typically the best deal, as we have to bump up to a higher resort level or suite to get us all in. But, I have researched it and often it can be only about $100 difference when you add in parking and car rental for the time of the stay.
Sometimes renting points from DVC member and staying in one of the DVC's properties can be even cheaper, from the research I've done.
I "think" they allowed the free dining for them last year, but I don't know. The good news staying there, though, is that you could make meals at the room without feeling like you were really going away from Disney to do it.
There are a bunch of ideas for reducing costs, like bringing food, relying on shuttles only, cutting back on days, staying offsite, cooking your own food, etc. Sounds like you're looking to find out how to do the "big trip" cheaper, in which case the ideas here would really help.