I just did this. I stayed Friday and Saturday on a package booked through Costco. Then Sunday and Monday on points at the GCH.
I made sure it was noted on both reservations,
DVC and Costco, for them to be linked. Then I called the hotel about a week before to make sure they were linked. When I checked in there was absolutely no problem. I never need to check out and back in. It might not happen this way all the time, but it can be done.