As far as running the numbers, as Dean correctly says, it's very much up to your individual habits and preferences.
While you say you don't like to cook on vaca, even just having cereal and toast for breakfast 5 days out of 7 is going to save you maybe $150 a year. The use of a fridge so you can have access to cold drinks instead of paying resort prices can be a huge saving if you actually look at the charges ( $2 for a soda, $4-6 for a beer). Individually they are small savings, but multiplied up over a whole holiday it does make quite a difference. IMHO drinks, breakfasting as above and maybe having a couple of meals like pizza (at lunch if you're taking a break from spending time round the pool, or you have a kid thats just too tired to go back out to eat after a day in the parks).
It's worth remembering as you become used to spending vacations at WDW it is less likely that you'll go to the parks everyday. All DVC resorts have some great pool and recreational activities. When you do make use of those facilities, it is possible that instead of buying pizza and fries from the hotel snackbar ( probably $50 for family of 4 by the time you include drinks all day) you might go up to the room (getting the kids out of the sun for a couple of hours is never a bad thing in summer) and slip a pizza from the freezer into the oven. IMHO it's hardly cooking.
While the above does offer some saving, I think something like $500 a week is a fair guess, it's really in you room charges that the finances come into it. Not everyone can only use Sunday to Thursday's cheaper rates, but there are a lot of ways to avoiding the high costs of Friday and Saturdays. If you can be flexible in the use of your points then this can make a huge difference to the costings. The points cost of two Sunday to Thursday trips is the same as one whole weeks cost. Obviously if you only EVER use Sunday to Thurdays for vacations your break even is going to be something like 30% better than if you calculate a whole week (7 days). If you only ever vacation for long weekends then your breakeven time is going to be seriously worse than either straight weeks or Sunday-Thursday breaks.
Just to be very simple in explanation let's say the $ cost of a room is $100 a night ( I know there are no DVC room rates at $100 per night but this is just for simplification and allowing that maybe someone would stay at a moderate or an All Star)
DVC two stays Sunday to Thursday at 10 points per night would cost $1000 for the same stay using $$$ or 100 DVC points
A whole week would cost points 5x10 and 2x25 so still 100 DVC points but $ cost would be $700
two stays Thusday to Sunday (3 nights) would be 60 points per visit ( 2x25 and 1x10) so 6 nights accommodation is 120 DVC points but would only have cost $600 if you were paying cash.
It's up to you to look into what you're likely to do in the future and use your own vacationing habits to fine tune any spreadsheet you use to get accurate data for your own circumstances. I hope that helps you a little in your plans. The more flexible and resourceful you can be with your points, the better the numbers will work in your favour, so do really think through things.