You can always drop hints. I got my father AND my father-in-law to go with me to a car show. Neither are "car guys". They both had a good time. They spent the whole time reminiscing.
"I had one of those when I married your mother", "I helped you Grandpa fix up one just like that"Yadda, Yadda.
The only problem is you won't be able to spend nearly the time you usually spend. A quick go-and-see for about 2 hours was all my Dad was up to. Kids and Grandpa's are not usually into all-day swap meet sort of things. It's worth a shot.
I must be lucky. My father in law likes cars as well. I get to have family days with him and my 8yr old son. We take poppy's 60 T-Bird to the shows look at the other cars and have fun you know just the boys. We will get to take my 70 sports roof some day right now its in the restoration stage.
So enjoy the family while you can because they are the important ones.