To follow up on Boog's post... I recall when it came time for my Grandmother (who lived with us) to quit driving.   She was driving one day, it was raining, and she hit a culvert with the car. My Dad decided it was time for her to quit driving.  She didn't take it well. Fortunately, us kids were teenagers at the time, starting to get our driver's license(s).  So, we - her grandchildren - got the job of being her chauffer.  We would take her to see her friends, and that got us driving experience.

To JR B, I think one of the things you need to look at is something to fill your dad's time - replace his tractor driving with something else. I don't know what that would be. But I think it is something you need to focus on.

You say his good friends have all died or moved away. This might be something you need to focus on as well. For times when you are not terribly busy, maybe take time to take your Dad to see those friends who have moved away.  Be intentional about this. You may need to plan ahead on this. This might be more valuable than you realize. Yes, it will take time away from your farming time. But looking back 20 years from now, you may be glad you did.  Also, Maybe look for ways for your dad to create new friendships.  Find ways for your Dad to keep in contact with his friends, thru telephone, on-line chats, zoom, etc. This might be something you want to work on after your crops are harvested. Just a thought.