We've stayed at all 3 with little kids (baby times to present), and actually went as far as making offers on BWV and BCV before RIV was a thing. (Now we own at RIV). We love all 3 but I would recommend RIV, especially if you're going to be in a studio:
BCV: pros:
close to EP, cons: no views, long walk to SAB pool. which isn't really laid out well for little kids. (If you're in a 1br, the bathroom layout in BCV and BWV is a little wacky - I feel like there's some wasted space there.
BWV: pros: close to both parks, kiddie pool and playground, Boardwalk area is fun; cons: no splashpad, hallways can be loooong especially with a stroller. One elevator bank isn't super close if you're walking to HS with a stroller, and sometimes you'll have to wait.
RIV: pros: terrific layout in studios (similar to VGF studios with split bath and 2 places to shower), if your toddler is in a crib there is usually a little space near the bathroom that's a little out of the way where they can sleep; nice views for after baby goes to bed. splashpad and pool are well laid out for little kids, excellent food, skyliner is fun. community hall is fun. (if you're there over Xmas you can let them know your room number and we got personalized letters from Santa back in 2021) cons: not walkable to EP/HS (but I find the skyliner to be more than adequate; we've stayed there 4 times and never had to bus to/from EP or HS)
If I had to rank studios: RIV, BWV, BCV
We stayed at Beach Club in November with a 4 and 6 year old.... the pool at BCV is cool, but really over whelming with young kids that are not strong swimmers.... lot's of different areas, the lazy river is really deep, the small slide that would be for the 2 year old is across the walk-way outside of the pool area. The large sandy area is fun, but there isn't a "splash pad" area for young kids. We started going to Disney when my youngest was just shy of 2 and he loved the pools that had the smaller splash pads so he could do slides. Of the 3 resorts you mentioned only Riviera has the splash pad area for young kids. Not sure how important the pool is? I will say the walkability to Epcot and HS is great from either BCV or BWV... BWV will be closer to HS. We love when we are able to walk back to the resort for a break!
We have stayed at BCV a few times starting when my younger one was a toddler (she is now 6 and a pretty strong swimmer). SAB is a huge favorite with my kids now, but it was challenging with a toddler because even in the sandy beach area, the sand was uneven enough that she would fall down and end up underwater because she insisted on walking in chest deep water. So I ended up crouching/sitting while she explored. It wasn't really restful.
ha yeah, we bought at VGF for the walkway. both epcot walks seem quite mild compared to the walk from VGF in Florida heat
LOL. We bought before the walkway, were super excited to use the walkway, used it once in December, and went back to using the boat "home." Monorail at rope drop, boat home FTW. (The boats to VGF are really only a pain if you have a stroller to fold, but they are the best kept secret... oops)