Since I do not know very much about off-site accomodations, I will assume that you want to stay on site. Consider asking this quesiton on the Orlando Hotels and Attractions Board if you are willing to stay off site. Depending on the season, you can find some nice places at very affordable prices.
IMHO, two rooms at one of the All Star Resorts will be the least expensive on site option for you. This will be especially true if you can snag a discount. Keep an eye on the mousesavers site for discount ideas. You can request connecting rooms (with an inside door in between the rooms) or adjoining rooms (next to each other). Disney won't guarantee this, but they do try hard to accomodate these request.
If you want to stay together in the same unit, consider a two bedroom unit at one of the DVC resorts - VWL, BWV or OKW. Of these three, OKW units are the largest. All of DVC 2 bedroom units have a fully equipped kitchen, two bathrooms (one with a large jacuzzi-like tub) and a washer/dryer. Rack rates for these can be quite expensive. You may want to consider renting points from a DVC member. If so, take a look at the Rent/Trade Board for more info.
You can also consider one of the two or three bedroom units at Disney Institute. I do not know much about these, but there are generally discounts available there.
Good Luck!
