Thanks for your advice...
If you are concerned about if he is healthy enough to travel, that is a question for his doctor. He would have to be in pretty poor shape for his doctor to suggest he should not go. Two and a half hours in a car is not all that long. We take my 93 year old mother in law at least once per month on a trip that long. We do stop half way at a rest stop and that gives her an opportunity to walk and stretch a little. In September, my mother in law, along with two daughters and a niece travelled by car to British Columbia for a weeks vacation. We live in Wyoming at 6000 feet and they had no difficulty going to near sea level and returning to altitude.
Also, we often visit the old family ranch, 7 hours from here and go over a 10000 foot mountain pass to get there. Again, no problem.
Some other advice you did not ask for: Life should be an adventure, and an elderly person should not be excluded from that adventure. Most people at that age welcome risk if it means improving the quality of their life.