Yes. I have felt that there's no harm in making that offer - the worst they can say is NO (with no counter), and you'll know what that seller's floor is. (I also do take a very zen approach to all of this - as with other real estate purchases - if it's a good match, the offer will get accepted and it will all be smooth sailing).
This might not be a bad idea. We started small, too, so that we wouldn't have too much sunk/committed cost if it turned out we didn't like to go to WDW once a year. Well, our "once a year in a studio or 1br once in a while" turned out to be "every 8 months or less" which in turn led to buying more points. You could always start with a smaller contract and go every other year, or for a shorter period of time, and see how you like it. It's less $ up front, and then you can decide later, after a few trips under your belt, whether you want to continue or buy more points.
And as others have said - think about your travel preferences. How often do you want to go to WDW? And do you really prefer deluxe, or is moderate or value good enough? Or what about an offsite stay? I can't remember - how old are your kids again? We realized we really wanted to stay in deluxe resorts on site because we had small kids and liked not having to spend so much time traveling. Our DD1's first trip to WDW was staying in a timeshare near Sea World and driving to WDW every day. We liked the space of a condo but we didn't go to Sea World once on that trip, barely made it to the condo's pool, and spent far too much time driving back and forth. (But this is how my family did WDW when I was growing up - it was definitely cheaper, but a bit of a hassle). Then we stayed in some deluxe hotel rooms as well as rented points a few times so we got a sense of what the DVC units were like, and whether we liked them enough. (We did) If you haven't rented points before, you might want to try that and see how you like staying in the villas. DVC isn't going anywhere, the resale market isn't going anywhere, despite the doom and gloom on these boards. A few months or even years of poking around and research isn't going to make you miss out on the "perfect" contract, but you might find that you like or don't like particular aspects of a DVC stay that may affect your decision.
Also - and this brings up again my question of how old your kids are - they're still young, right? We were easily able to hunt for the best deals, and take trips on short notice, when our kid(s) weren't in real school. My oldest is now in 3rd grade in a pretty rigorous school, and they don't take too kindly to pulling your kid from school for a week because you found a great 30% off deal on a hotel. And I know it's just going to get worse. So now we are limited to school vacation times. The summers aren't bad, but if you want to take a trip during President's week, Easter, Thanksgiving or Christmas, there are no hotel deals to be found. So that played a role in the timing, as well. (Although you can still rent points, you just need to find someone renting with the home resort you want, *and* try to reserve as close to 11 months as you can).