If you request a 2 queen bed "2br" at BCV, and it's available, it's a room type (not just a request), so you should get it. Similarly, if you go to VWL and get a dedicated 2br (NOT a lock-off) you will get the 2 queen beds.
Alternatively.... Do MIL and Mom like each other enough to SHARE the queen? Or what if they shared the king, and you and dh took the queen in the 2nd br? I would think that for the amenities of the master suite, they could learn to share a whopping king! Besides... one person in a king is just a waste, when you have so many folks suffering the wrath of sleeper sofas!
We are staying at BWV for 8 nights and BCV or SSR for 4 next summer, and I'm a bit worried about those sleeper sofas myself. We've never used them before, but this year we will need to. HOWEVER -- we are just putting our lightweight, deep-sleeping kids (ages 5 to 9) on ours. Our kids love to use sleeping bags too, so if push came to shove, we could always just put their sheets and blankets on the floor and they would think "COOL! We're camping!" We have a sleeper sofa at home but it is a pretty high end version amongst sleeper sofas. I find it comfy for a night, tiresome for anything more than that. I mainly hate setting it up, taking it down -- how it feels actually is a bit secondary to that!
While I'm at BWV and BCV next summer, I may just "test out" the sleeper sofas for future reference. I'm of moderate mass (about 150) and ht (5'8") and pickiness, so I'd be somewhere in the average! FWIW, my teenage nieces have used the sofa bed in the living room at OKW many times and say it's great.... I do not know, however, if all sofas are created equally at all
DVC resorts. Would need to know the "grade" of the sofa and mattress -- they do come in differing quality levels.