Well there's definite advantages to both

resorts !!!
( don't know if you a member staying on points - whether or not you can pool hop depends upon that ).
BLT newest
DVC & great access to MK, monorail and GF, Polynesian and boats to WL and Fort Wilderness can offer you much in getting around to explore other resorts; you can see Electric Water Pageant nightly from any of the Seven Seas Lagoon/Bay Lake beaches, Fort Wilderness has nightly campfire with Chip & Dale and movie, WL has walking trails to Fort Wilderness and Hidden Mickey search. Polynesian has few kids activities at kids desk in lobby sometimes that you can walk in and do like lei making; GF has a ladybug release day for kids ( think it maybe Thursdays )
Staying at BCV allows you to use Stormalong Bay and there is also some kids activities usually during day at BCV & campfire on beach (some nights during week iirc), Beaches & Cream Ice Cream, it's an easy walk ( surrey bikes are available to rent too ) around Crescent Lake to YC/BC, Swan/Dolphin and BW/BWV. BWV has Community Hall adjacent to villas quiet pool where your kids may find some fun activities to do, some are organized by CMs and others are just available to do anytime you drop in. In early evenings there are Boardwalk Entertainers out and about on boardwalk around village green area or they'll be in BW lobby if weather is bad ( magician, juggler, etc. - it varies) and there's some carnival games on boardwalk as well & Seashore Sweets / Bakery for ice cream & amazing baked goodies.
If you're looking from adult time without the kids I think your youngest may be too young for one of Disney's evening childcare clubs, you're only option may be in-room childcare; Disney recommends Kid's Night Out. I think minimum age requirement is 4 yrs. at the resort childcare, but there are clubs at YC/BC - Sandcastle, WL - Cub's Den, AK Lodge - Simba's, Polynesian - Neverland Club and Mouseketeers Club at GF. Swan/Dolphin also have; not sure on their minimum age requirement - it may be different than Disney-owned resorts.
Can't go wrong with either BLT or BCV ! Have fun planning
