Well, first off, since you are splitting your stay you will be looking at two trips to the market. Check out/check in times are pretty far apart. Perhaps just the basics (bread, cereal, bagels , PB&J and such) for your 2 day stay and a trip to market with a more extensive list for the 7 days. If transportaion is an issue I think Albertson's lets you fax a list with pick up date/time and you are in & out in less than 5 minutes. That would work well if you need to take a cab.
Since you have 5 people I assume you have at least a partial kitchen at BCV. Breakfast at the resort is a no-brainer. Saves time AND money. You are on vaca so the meals you make should quick and easy. Box mac 'n cheese, hot dogs, sandwich meats, pasta/sauce & throw in a pound of hamburg..you get the pitcure. I stay in Timeshares w/full kitchens when I go to WDW and I basically make my menus and shopping list before I go. Any meal I make takes no more than 20 minutes to prepare and although we eat about 1/2 our meals TS at the park/resorts, we save a TONS of money by preparing meals at the resort. Also, people often mention they have packages of non-perishables sent to the resort before arrival. That could be an excellent option for you too.
As far as on-site meal deals go, I think the cheapest buffets you can find are the way to go.