I just wanted to support what Sherri posted above. While you continue to get well informed and to think things over carefully, work with your dad to make sure that his friends, co-workers, neighbors, alumni, church/synagogue members, club memebrs, etc. know of his need and of the possibility of living donation. This does mean giving up some privacy, but can be worth it. There may be a good donor of his own age right around the corner who would gladly step forward once the need were known. Some folks have received a kidney from their waiter, manecurist, bar-tender, grumpy neighbor, etc. as soon as the need was communicated. You could stand by as a "back-up" should this second transplant eventually fail years from now. I think your Dad would be happy to find a donor who (because of age and family status) might be better able to handle negative after-effects IF they should happen. So don't feel that you are the ONLY option.
best wishes,
Fr. Pat