We stayed in a 1-BR a couple of years ago and toured (saw all unit sizes). The 3-BR is indeed the size of a condo or apartment that one could live in... perhaps 1,500-1,600 sq ft. The 3-BR's are really made up of connecting 2-BR/2-bath and studio/bath. After a suite hotel, you'll be amazed at this 3-BR/3-bath luxury unit!
--- king MBR suite w/double jacuzzi & separate shower
--- 2nd BR with 2 double beds & standard bath
--- 3rd BR with queen bed, sleeper sofa & standard bath
--- queen sleeper sofa in LR/DR area (spacious, not cramped)
They call these "sleep 10" but if you used all the sleeper sofa beds, they actually sleep 12. The studio (3rd BR) will have its own wet bar, microwave, mini-fridge & small table/2 chairs. If you give this room to your MIL & BIL, they may enjoy the privacy. Or they may prefer the second BR with two regular beds, rather than one bed and one sleeper sofa. Either way, if they share a room, your main LR/DR/kitchen will be free, with no one sleeping there.
Very nice. There's a big screen TV/VCR in the LR and smaller TV's in each BR. Have a fun time - it's a gorgeous resort!