If you've used turtle wax for 35 years on your monaro, and the crappy paint they used back in the 70's has held up well, with such TLC, then continue with the same on your Caprice. Unless of course you can't be bothered with the effort that polishing requires, in which case use a ceramic coating after some paint prep. Careful DIY should get 90% of what the pros will achieve. Good enough i say.
Either way, being at the point in your life, that many us are, mortality must come into focus. There is no point in pampering your cars as, statistically, healthy people in their 70's wont be around to admire their efforts in another 35 years. And from what you've said, your son doesn't look after his cars, what with burger wrappers and lack of cleaning... So drive them, drive them all.
Me i'd be driving them all the time. OK, maybe not the monaro when its pissing wet as i hate to clean (and i will). There is more to enjoying vehicles that washing and cleaning them... Drive them
and if they get devalued somewhat due to putting lots of kms on them, well, then maybe your son should have had a bit more interest in cars and a little bit more of the old man's attitude in his vehicles