Fwiw, I think it's worthwhile to try out the z-rest, but my kid definitely does not sleep as soundly as all of your kids seem to. It's not just a matter of falling asleep, it's a matter of waking up multiple times in the middle of the night. Car camping, I can bring a couple pads to add some extra cushion and he does fine maybe waking up once in a while because of unfamiliar surroundings; in the crib he never wakes up in the middle of the night.
We all need sleep after a day of hiking, and if this will help him sleep at night and therefore keeps him from waking me up, so be it. It's not like I can tell a crying 2-year-old to suck it up in the middle of the night, when ultimately, he's going out because I want to.
I don't think I'm going to go with Bender's for the time being though, it just doesn't sound sturdy enough, although I loved the idea of using it for myself ;) But then again, the toddler is still going to be playing in the tent with my air mat even if he had his own. I will try the zrest because everyone else seems to have such good luck with it, hopefully it will work.