something to consider:
the big draw at the BCV is the pool. if you are going in december, it may be too cold to use it.
of course, the BWV kiddie pool would also be too cold.
at the BWV, the other "to do" options include community hall (crafts, ping pong, games, etc), nighttime street performers (magicians, etc), surrey bike rental, & carny games, various restaurants and food kiosks. of course anyone can visit the BW, but there is nothing like having it all within a few short minutes of your villa (especially nice if one child - or adult

- wants to sleep NOW, feels ill, etc).
i agree with others that AKV would also be a good choice. tho you cannot walk to any parks as with the BCV/BWV, the kids would probably love having exotic animals in their "backyard".
BUT.....if you are thinking about the end of this year, your choice will probably be determined by availability. nov/dec is a very popular time for
DVC, and the smaller DVC resorts have very limited villas (especially any other than 1 bdrms)/nights available long before the 7 month mark.
as far as villa size: obviously a 1 bdrm, with a full kitchen, washer/dryer, 2 TVs, and separate living room would be best. the little ones can nap while others watch TV, the full size fridge can be invaluable for that many ppl, and laundry is much easier as well as less time-consuming.
good luck!