Where are you staying? Which resort?
In BWV the second bedroom is actually a lock off studio unit. The door to the one bedroom is in the living room, so one bedroom on each side of the unit. The master bedroom has a king size bed/jacquzzi tub room with a vanity and large closet. The living room has a pull out sofa, full (but small) kitchen, front hall closet, washer/dryer & full bathroom with a shower stall. The 2nd bedroom (studio unit), has one regular bathroom, vanity outside of the tub/toilet room, small kitchenette, with mini fridge, wet bar sink, coffee maker, microwave and if I remember correctly a toaster. There's a queen size bed and a pull out sleeper sofa that will definitely sleep two kids. There's also a table and two chairs and an set of drawers with a tv set, and usually a balcony off each room.
Personally, I'd put my sister and her husband in the studio unit bed, with her two kids on the pull out sofa, so they have their own privacy, like a full room/kitchenette to themselves, and I'd put my two kids on the pull out sofa in the living room, while my husband and I took the master bedroom.
Happy planning, and good luck!