If you want to do a
charitable donation, there are several ways to do that.
One is to offer the points to a charity of your choice which is having a fundraiser. They can use the Disney reservation for a silent auction item or raffle item. If you do that, you need to be very specific about the expiration date of the offer -- you want this to be a benefit, not a problem, for the charity.
Another approach several DISers have used is to contact
Give Kids The World -- a wonderful charity that provides
Disney vacations for kids with serious medical conditions. GKTW will NOT use your points for those kids -- they have their own facility which was specifically set up to care for these kids.
What they will do is make a reservation available to some of their many volunteers who contribute so much time and effort to the charity. Here's a link to their website if you want further information:
http://www.gktw.org/
Depending on how many points you have and when they expire, GKTW might be the simpliest. Give them a call, get a couple of dates and make the ressies, and you're done.