My wife & I are both in our mid-50's, and we stopped going car camping a few years ago largely because of the lack of sleep and difficulty getting into and out of our tent. Our last trip we were so tired that I was hallucinating on the drive back home & we had to pull over on a mountain road to take a nap before we carried on.
Even the nice mattress suggested in @shemseger's answer didn't solve the problem (we have a Coleman queen sized, very comfortable to sleep on, not so easy to get down onto or back up from). My biggest problem is arthritic knees, and to a lesser extent, arthritic back. We've since bought a very nice cot from Cabela's and a very nice Thermarest NeoAir Dream mattress for me. We've yet to take them camping, but being able to sit down on the cot to get dressed/undressed, put on or take off your shoes, is a very-very nice feature. The air mattress just makes it better. My wife is much more spry than I am, so sleeping on a good air mattress (which we have, just can't remember what it's called) on the ground is still OK with her, but I think if we ever get back into camping, a cot for her is in the works. My brother has almost the exact one we bought, and she slept on it last time we visited, and quite liked it.
As far as tents go, ours is still an older, fairly low (as in you can't stand up in it, not even my wife who's 5'-0"), style tent. If we were to start camping again, we'd look at much higher tents so there's standing room, at least in the center. It just makes things easier to do when your mobility is somewhat limited.
The recommendation for good chairs is a very good idea as well. My arthritis makes sitting at picnic benches unpleasant pretty quickly. We have a couple of very good camp chairs, as well as one of the one's shown in the answer above. I don't particularly care for it, but my wife will fall asleep in it in moments if given the opportunity.