Oh, damn, Steve. I didn't see your post before blathering about the swanky hotel. Truly sorry you and Fred are going through this, and I know how hard the decision is to make. I still think about my last dog BillBob all the time and was looking just a couple days ago at the last pics we have of him. He looked awful with lumps and his front paws were so turned in from arthritis that I cringed. He was 14, though, and we had a lot longer time to make the tough decision.
The only advice I would dare to offer is to go with your gut and if you think he is really unhappy and uncomfortable do what you have to do. It is incredibly quick and painless for him. But if he is OK and not hurting and just has a different, sleepier life ahead for what time he has left then hang out with him while you can. We sure had old BillBob hobbling around for a long time, and carried him up and down stairs even toward the end, but the vet said he wasn't hurting and he seemed happy to be with us still.
Good luck buddy, and take care of yourself too.