I've been married for 39 years and my father in law was riding long before I met his daughter. Triumphs, 2 Moto Guzzi, and many dual sport bikes of differant flavores. Hodaka and Bultaco dirt bikes were always ridden by him or the kids.
While my mother in law was still alive they did a lot of riding around central N.Y.
He is 89 years old now. Yesterday he told my wife during a phone call that he really enjoyed the ride he'd just finished on his Yamaha 250 dual sport. He said the only down side to the bike was they seem to be making them taller now and his leg doesn't like to swing that high. With 3 knee replacements ( yep 2 on 1 side ) I'm not surprised.
Sure hope I'll be in good enough condition at his age to still be riding. Maybe I should settle for just being able to walk at that point.
Here's to you Dad

. Ride them while you are able.
On a side note I suggested he look at the Honda Rebel with 300cc and low seat height.