Thanks again, everyone, for all the great ideas.
The winner thus far is the hammock. I know he doesn’t have one, and it sounds great. Going to stop by REI tonight and see what’s available.
Something anti-bear related.
There are hammocks you can get that have their own support (no trees required). The one I’ve seen takes up a fair amount of space in the car, but it might be an option to keep in mind.
Here’s a really cool hammock, but it’s kind of expensive.
That’s a great gift. It’s a huge camp hit, is light enough that a very determined backpacker could make the effort to make it his luxury item, and is one of those things that the giftee would never get as it’s always last on their personal shopping list because it’s not absolutely necessary.
I can’t follow the links at work, so I don’t know if these are lounging hammocks or sleeping hammocks, but I simply can’t sleep in one. If these are sleeping hammocks you should see if your dad has tried one and if he likes them.
That’s not a hammock! That’s the cockpit of a futuristic spaceship! :eek:
Actually, I love my backpacking hammock. That’s a great idea. Consider getting a double-wide so your parents can snuggle. Or not, if it squicks you out. 
Does he have an axe?
GPS
Rope (e.g. does he do any climbing or rappelling?)
Maybe too late, but one of those bug nets that encloses your head is a life-saver if you happen to end up camping during a bad skeeter/black-fly/no see-um season.
A compass. You’re not really camping unless you have a compass.
This is car camping. If you need a compass to find B21 and the path to the outhouses then you have other problems.
Does he have a compass altimeter borometer watch from Casio? Costco had my latest one on sale for about $90 6 months ago. These are great for camping.
A boorometer would be useful at parties too.
And if you are still looking, I’d suggest star charts and maybe astronomy binoculars. Actually, any decent binocular works OK for casual star gazing. Many campgrounds are some distance from towns and light glare, making star gazing a good camping activity.
Since he’s a car camper not really a big deal but I love this chair I bought at MEC, it so small fits in a pack. Very strange looking but works great.
I knew that it would be that chair before I clicked the link. Count me in as another recommendation for this chair. It was the best purchase I made in 2011.
My GF bought that this year and she loves it as well.