Long before I owned my own.... I borrowed my parents motorhome once in my early 30's. Class A, not a Jayco, but still related. I am more meticulous and careful than even my father, also a gearhead, and most of my automotive knowledge I learned from him.
The trip was a disaster.
Even though I was keeping distance from other vehicles, the windshield picked up a rock chip.
My driveway was really, really tight, and I was backing it in before my other half got home from work, trying to make room so the garage could be accessed. The sun was in the mirror, and I rubbed one of the compartment doors with a piece of short garden fencing that I couldn't see in the side mirrors. It left a mark that I couldn't get out with some gentle buffing.
Of course I returned the motorhome full of fuel, freshly washed, the interior cleaned. I said I'm sorry, I'm willing to pay for a new windshield and bodywork/repaint of the bin door that had a scrape. My dad said don't worry about it (although I know it ticked him off).
But I'll never borrow someone's motorhome again after that!!! I felt so awful.
I'd say if your son didn't offer to replace/fix what was damaged during HIS trip, then the next time he asks, it's a NO.