If you'd be interested in your DD taking a class behind the scenes, you could get tickets through the YES(Youth Education Series) program at Disney. Tickets are close to 40% off rack rates and you would get them for all three of you. It would involve a class for 3-4 hours early one morning. Registration for summer classes should be open mid-February. 7 day hoppers through the program are 199.15 each, so around $600 for the 3 of you. There is a whole thread on it here
http://www.disboards.com/showthread.php?t=2332767 It's a long thread, but if you read through the last few pages, you'll get a lot of info.
I would use the room only discount PPs have mentioned. I believe it lists value rooms at around $90/night, so 7 nights with tax around $750
Are you sure you want to drive? What is it, maybe a 14 hour drive?

And the gas will cost you $300-$400 round trip on the low side. I bet you could get a good deal on airfare, and if you stay onsite, you get transportation to/from the airport and to/from everything Disney.
Food--I wouldn't get the dining plan. I would plan out what you want to eat. There is a site that lists all the dining places, but I don't know if I can post the link. DS and I split meals a lot until he was 13 or so. You can do character breakfasts, as they are cheaper than dinners, but have the same characters.