Android- I haven't used a Coleman 2 burner stove since the one my family bought in the early 80s.  Don't have any experience with it's fuel usage.  Of course, the fuel consumption depends on what you'll be doing.  How many meals a day will you cook?  Will cooking consist of just boiling water, a giant fish fry, baking, or what?  Off hand, I would expect that for 2 people and 6 days, 1 gallon of fuel is probably overkill, but it's probably better to have too much than too little.  If there aren't any burn restrictions, you can reduce the fuel you bring and plan on cooking over fire as a backup.