I would stay at BCV given the diversity of ages and groups in the party - close to Epcot and Disney Studios and the Boardwalk. That is a huge pro to me combined with the best pool complex on Disney property - Stormalong Bay. Also, given the size of your group and again depending on diversity, the restaurant choices within the area are the best by far within WDW - so much variety and choice.
"Major" Shortcomings of BCV:
Shares Disney Buses with other Epcot resorts (not a big deal in my mind but has been raised as a point)
No direct transportation to Epcot Main Entrance - you need to walk through the Int'l Gateway and through part of World Showcase into the "back" entrance. If you do not relish the walk (or parts of your group do not), they would need to drive to Epcot front entrance (not a huge deal but something to keep in mind)
You could get a room with a small balcony - again may not be an issue but has been for some
http://www.disneypix.com/2000ft/Roll2/Roll02_017.htm
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At VWL, as mentioned, you are close to the Magic Kingdom by boat launch, there are nice views to Bay Lake, the lobby theme is amazing. The room sizes are the same as at BCV. The bus transportation is good in my experience. If so inclined, you can walk or bike over to Fort Wilderness which has stuff for kids to do. You can rent watermice for riding on Bay Lake and 7 Seas Lagoon, you can view the EWP as well.
"Major" shortcomings at VWL:
Boat launch dock to MK is a decent hike from VWL
Not within walking distance to anything - i.e. somewhat remote
Since it is remote, does not have anywhere near the dining options that a stay at BCV gives
http://www.disneypix.com/2000ft/Roll3/Roll03_006.htm
I am sure others will chime in as well, but I would stick with BCV given the diversity and size of your group
Thanks
jaysue