At age 62 I am poor on the trails but ride roads and paths at least a hundred miles a week. For that perspective, I suggest:
- be happy he wants to avoid couch captivity
- start him on the most mild trails within fifty miles of home -- like warm up bike path expeditions at first
- take the lead go slowly and stop often
- do not take him on trails tougher than he can handle -- if he insists, he can go without you.
- give the old guy, stubborn as he may be, credit for at least a few brains.
- bring flowers to the hospital as necessary