When are you going?
If it will be during the warmer months and you'll be using the pool a lot I have to say that in our experience (having kids ages 2, 4, and 7) the BCV is a great choice. Stormalong Bay is incredible for young kids. One entire section is dedicated to the little ones, with a zero entry sand beach and sand bottom pool that is only a few feet deep. It is wonderful for the really young kids to play in without having to worry about them too much. It also helps that the BC is an incredible resort. There is also the creek by the BCV quiet pool where you can spy fish and turtles, and if you are lucky even an alligator! BCV has direct access via boat to Epcot and the Studios.
Second choice would be VWL, especially during the cooler months when you won't swim as much, or if access to the MK is your top priority. Not to say that the pool at WL isn't very nice, it just isn't as exciting for the kids as SAB. There is a huge kiddie pool at the WL main pool. Also, the Hidden Springs pool area over by the villas is THE most relaxing place in all of WDW. Great quiet pool for the kids, but even better for the adults. Ahhhhhhhhh. The WL has a bubbling spring in the lobby with a bridge over it, and kids LOVE to run over that bridge........again, and again, and again, and again.......you get the idea. The brook goes out of the lobby, outside and down a waterfall, ultimately into the main pool. Very cool, as is the guyser. There are lots of activities scheduled for the kids as well, like duck races, games on the beach, etc. There are always real ducks swimming in the pool and kids get a kick out of that. There is a playground on the beach, and renting Sea Raycers on Bay Lake/Seven Seas Lagoon is a lot of fun for the kids and kids at heart in the family. There is a ton to do. The boat to the MK is wonderful. Yes, it can take anywhere from 15 to 25 minutes depending on how long you wait, but the boat ride is entertainment the kids love in and of itself. You can't go wrong with the WL any time of year.
SSR is nice, and the zero entry pool and Donald play area (small but nice) is great for the kids. However, lacking direct access to the park and being as spread out as it is I can't recommend SSR over BCV or WVL.
FWIW, we love BCV and VWL so much that we no longer decide between the two........we just split the stay. We get the best of each resort, and plan days in the parks according to which resort we are in.