To book for December, you are probably too late anyway. But it's a dangerous idea to buy points for someone else to use, especially overpriced direct points. There is story after story on these boards of family members not going for whatever reason.
Disney as a hotelier, and
DVC in particular, have limitations. It's hard to recommend anyone spend 60K on something they don't know if they like. All DVC rooms have minimal housekeeping, cheap TP, no real service to speak of. Many have bad views, some of them are really showing their age and are among the worst in the Disney portfolio. IMO, as hotel rooms, it's hard to reconcile many DVC rooms with the cash rates they (and the cash equivilant) demand. And then there's the booking system.
There's a lot between spending 60K and not seeing your family. You could rent DVC. You could rent an Airbnb. You could go somewhere that isn't Disney. Heck, you could rent a confirmed reservation for this trip and start there.
I view this whole plan as a lot less risky if you are just buying resale SSR points. If it doesn't work out, you sell. But if you're buying SSR, you better know how to work the system, which is a job in itself.