Sure they do. You can start with a small contract and add another small contract down the road. Just know that with a small contract you might not get a
DVC vacation every year, but maybe every other, if you do the banking/borrowing thing.
For example, a studio at OKW from July 7-14 is 109 points. OKW has the least expensive point per night amount, July is one of the busiest seasons. That same studio at OKW for January 1-8 is 80 points.
Since you have a 10 year old, one can assume that you will be somewhat tied to the school vacation times to do a WDW trip...at least for a few more years. School vacation times tend to be the most expensive "seasons" so keep that in mind.
If you decided that WDW would be an every other year trip, probably the least amount of points I would buy would be 60, and 75 would probably be even better if it was within your budget to do so. That would give you 120-150 points every other year, which could get you a pretty nice vacation.
One of the things DH & I used to do before we bought a second contract was to spend the weekend at a regular resort and then move to the DVC resort on Sunday night. So we'd arrive on Friday, stay Friday and Saturday night at a moderate, and then on Sunday move to the DVC resort. Friday and Saturday nights are the highest point-wise, so avoiding spending points on those 2 nights saved us quite a bit, and plus, I kind of liked experiencing 2 different resorts. For some reason, it made the vacation seem longer and moving wasn't a big issue for us. If we had a car we just packed it up and if we didn't have a car we called Bell Services and they moved the luggage.