When we had a soft floor camper our kids slept on stretchers but they had a thin foam mattress on top (came with the oztrail bunks) for insulation, I think they'd have been fine sleeping on that foam mattress directly on the floor actually. We all had self inflating mattresses in tents for a bit too, I don't think it was any colder really (just not as comfy as a thick camper mattress for us lol).
Now the kids have swags and we recently brought a hard floor. They're aged 9 and 11 (just about) so are more than happy to sleep out on their own, but the idea is that if the weather is nasty we'd just roll the swags out in the tend on the hardfloor.
It depends how old your kids are, I think with several different ideas (for a bit of insulation between them and any floor) they will be fine. If they're 8yrs onwards then swags might be a good considerations as well, particularly as they get older and like more independence, it makes it a good investment. Really you wouldn't even have to roll the swags up, you could just throw them on your CT bed (if they were staying clean and dry in the tent)