If you couldn't get a one bedroom villa (the BCV one bedroom villa does not have the sleeper chair, so you would have to bring your own aerobed or book one of the villas that have the sleeper chair - OKW, AKV or BLT) with 77 points, you could use those 77 points to book as many nights as possible and pay cash for the remaining nights. Or get a transfer from another member to book the remaining nights.
Since your youngest (of three) is three or older, you need a one bedroom villa at a minimum.