Leane, have you spent much time on the DVC forums? There are some real experts over there in terms of the ins and outs of the financial side of DVC.
TOO much time
Those resorts in my signature are those at which we have points. My DH and I absolutely love BCV.

So far we've only stayed at BLT once. We thoroughly enjoyed our stay and love forward to using our points there as well. We have vacations booked there for Dec. and May.
I really look forward to hearing about your stays!
The contracts are for so long that I would buy where you think you would be happiest without considering the ages of your girls. Their preferences might change several times over. Both resorts do have much to offer them at their current ages though. SAB is fantastic and we really enjoy Dune Coves pool as well. The pool at BLT is nice and the slide is fun according to my DH. Both resorts offer activities for children. Both have many restaurants in their respective areas that are easy to access. That is an important part of Disney trips for us. Most people would consider the views at BLT far superior to BCV. Our villa in September had a drop dead view of Bay Lake....fantastic. However, we also enjoy the quiet views at BCV.
If you had to choose a lagoon or mk view which would you? They have one on hold both are available... I need a room for the 27th.
When you say book without the tour, do you mean buy or just book a single trip through Disney Reservation Center? I personally wouldn't buy without doing some research. We did the DVC tour in 94 or 95ish but didn't buy until BCV went on sale in 02. We bought there before it opened but had done quite a bit of DIS research.

Since the two resorts you wish to buy are both open, I would consider trying them both or at least visiting them since you have a trip coming up soon.
Decided to go this weekend to see them. Can't stay on the resort but we are going to tour them. I have a feeling it wont help
I am torn between the two terribly! I asked our guide if we could do 100 BLT and 80 BCV he said he didn't think they would but would call back. Called to say they will. Someone on tgm site suggested a quick trip. I looked up southwest and away we are going. We have family in cocoa beach and friends in tampa so we will stay on one coast or the other
I FROZE today it was 35 degrees when I left for work. So we may just decide this weekend. It would take care of the room problem on the 27th and the contract is exactly what i would have built myself...
One big advantage of BLT IMO is the second bathroom in a one bedroom.
Very convenient.
Don't forget to include the cost of yearly dues in your calculations.
Just to get on topic

, if there were to be a GF DVC, would you buy there?
OH HECK YEAH SIGHT UNSEEN
But for me this is a vacation investment.
Good luck with your decisions.