Actually, the maintenance fees will probably cost more than that over the next 40 years, if one anticipates a 3% increase per year. Annual dues have gone down recently, but 3% is a reasonably safe estimate for future planning purposes. Of course, hotel room at WDW have gone up more than 5% on average in recent years (but many discounts are available via annual pass, Disney Club, etc.).
DVC is targeted at families that want to enjoy what Disney describes as "home-away-from-home accommodations". DVC provides a significantly different level of accommodation than Disney's "value priced" resorts. Studios are a premium version of the "deluxe" hotel rooms. For example, at BWV (BoardWalk Villas), the studios are comparable in size to the regular rooms at the BWI (BoardWalk Inn) with the addition of a wet bar, undercounter refrigerator, and microwave at the BWV. However, the normal room limit for a BWV studio is 4 guests (plus one child under the age of 3) compared to 5 guests (plus one child under the age of 3) in the BWI. The one-, two-, and three-bedroom DVC units provide condo- or townhome-like facilities (full kitchen, washer/dryer in the unit, multiple baths in larger units, etc.) but require much more points than the studios. Guest limits are 4, 8, and 12 for these different size units. For your family size, you would ultimately need a two bedroom, so the 220-250 points per year would not go very far, certainly not for the length of stay you are currently doing at ASR. For you then, there is little or no economic advantage of DVC compared to staying at the All-Star Resorts, at least in terms of current costs for the value resorts. Two regular rooms at the ASR would be less expensive than any stay at a DVC facility, even in a studio. This might be offset in part by reductions in the cost of meals if you choose to do a lot of cooking yourselfs, but I never count on this since for the two of us, eating out is a significant part of the vacation experience.
We bought into DVC (via resale at BWV) after staying at the Disney Institute (a "home-away-from-home" resort which has been around since the early days of WDW) and the BWI (renting a refrigerator to provide some limited in-room breakfast fixing capabilities), so we knew we wanted this level of accommodation for future visits to WDW. We like the location and convenience of being able to walk to two parks (Epcot and MGM) and also take advantage of the entertainment along the BW. We will generally stay in a studio and fix only breakfasts and some leftovers in the room, so the larger units are less important to us than stretching our 220 points/year to provide at least two weeks worth of visits to WDW. Even this takes careful planning, since weekend nights (Friday and Saturday) have significantly higher point costs than the rest of the week (generally, more than twice as expensive in points). We will also stay at other DVC properties at Vero Beach and Hilton Head Island as alternatives to WDW stays. For us, the economic break-even point on our point purchase comes quickly, since we get about $4000 worth of accommodations for our annual dues plus the lost earnings on the money used for our point purchase (we paid cash rather than financing) which together total about $1600/year. We will have recovered our initial investment in about 6 years just from the annual savings, assuming that we would have used the earnings from the funds used to buy DVC to finance vacations instead. The $4000 estimate of the value of our accommodations is based on what we would be paying today for comparable accommodations at BWI or BWV during the seasons we visit and the length of time we stay during each visit, not what it would cost us to stay at one of the value or moderate resorts at WDW, and takes no account of future increases in hotel room rates. So for us, the economics made sense. For your family, they very well may not, since the initial investment (forgone earnings) and annual carrying costs (for dues and possibly financing) may be much more than your annual costs to vacation. That's one of the nice things about WDW today, there are such a wide variety of accommodations to fit the needs and desires of such a wide range of visitors.
Ralph