the cheapest if definitely FW - it does not have 2 bathrooms - otherwise - it is fine.
I happen to love OKW - but it is not close to a park - so bus transportation to the theme parks and water parks. there is a boat to DD. It has the biggest 2-bedroom.
BCV and BWV are within walking/boating of both Epcot and Studios plus the other Epcot resorts and BW area- and are very popular because of that. All other transportation is by bus.
VWL - this because of your children ages is probably your best bid. You can boat to the MK, Cont or FW. All other transportation is by bus. This is one resort where is helpful to learn the bus schedule. One of their buses goes to the T/T - you can use it to get to both Epcot and MK.
I really love them all - favorite is OKW - but that is probably more to due to the fact that when I joined it was it - the others were built later. Very relaxing...
my least favorite is probably BWV - if you love action you will adore this place - if you want to relax and feel miles aways from the action you will hate it - just a matter of personality.
VWL is one of the most beautiful resort at WDW - but people who like in the western pacific mountains don't like it - because it is like home to them (on the whole).
go look at the pictures - only you can decide what is best
www.dvc-resorts.com
You can rent from a DVC member and save you some money - but even then a 2-bedroom is expensive. Go back to the disboards - and go almost to the bottom - click on DVC rental/trade for more information about renting points - read Doc's FAQ first.
I would go with FW just on price.