I would recommend renting the points and donating the proceeds. If you rent 50 points at $10 per point, that's $500 which is a very nice donation.
I'd try to offer the points for transfer to another member rather than renting a reservation, because that is a much quicker, simpler, and easier transaction. They pay you, you transfer the points, you donate the proceeds, and you're done...no longterm involvement with someone's vacation plans.
The other option is to offer a future reservation as a silent auction item, or even better, as a raffle prize. The problems with that approach are that they involve much more effort, and you are still only offering a small part of the cost of a vacation. If you could put your points together with airfare, and possibly tickets, you'd have a very marketable raffle prize, but I wonder how well lodging alone would sell.