We still have a little time, what if you reasigned the people you are worried about new SS's. I am willing to do one and I bet others are too. That way hopefully nobody is without a gift one the 12th. I know that doesn't solve the problem of people not following through but Christmas is a bad time to be disappointed. If they happen to get 2 gifts well that's better than none, and then maybe you would be able to tell who followed through and who didn't after the swap and deal with them on future swaps.
I am shopping this weekend and can mail Monday morning if this would help. Just send me a PM>