You also need to think about your vacations in the longer term. It sounds like your kids are young, so having them in a fold-out couch and sleeper chair works. Will that continue to work when they're teens? Of course, there's always the option to add points when you "graduate" from a 1-Bdr to a 2-Bdr.
But I digress...
160 points doesn't seem to compute for your needs. The stays you describe seem to indicate you'll need more points. (I think 160-point contracts are so popular because it's the minimum number of points to purchase, and people just make it work. Mostly, this number of points will work for folks who take shorter trips, don't visit every year, and/or who stay in studios.)
I travel with a teacher, as well, which means that most of our trips correspond to the Magic Season (summer break) or (gulp) the premier season at Spring Break or Christmas. Sounds like you're lucky on that you get a longer Thanksgiving break. (Ours is only 1/2 day Wednesday and Friday of Thanksgiving week.)
Also, don't assume that you'll always be able to get a value or standard view villa at AKV. These are limited in availability. If you don't have the flexibility to change your dates because of your school calendar, you may wind up in a Savannah view on some trips, as these constitute most of the rooms at AKV. Also average out the fact that you'll want to (at least occasionally) stay at other resorts, and villas at different resorts require different numbers of points. You can very effectively use banking and borrowing to account for these fluctuations, but you don't want to be in a situation where you're
always borrowing from the next year's points.
You also shouldn't assume that the points it takes you to travel this year (2011 or 2012
point charts) will be the exact number of points it will always take.
DVC can reallocate points. The total number of points for all rooms for the entire year can't increase, but DVC can change points by season, room type, day of week, etc. You'll want to have a few extra points on your contract to cover this. (For example, if you think your annual vacation will be 161 points, you wouldn't want to buy exactly 161 points.
Only you can decide what your exact vacationing habits will be, and so you're the one that will have to decide on the exact points you need. We've added on twice since buying in 2006 as our vacation habits have changed. Mostly, this was wanting bigger villas (to invite family and friends), and longer/more stays.
Now, with all that said, for a one-week trip in a 1-BR each year, our 250 point contract seemed to work well. You results will vary.