Okay, I know this is an older thread, so I am probably late to the party.
We have a Kodiak Flexbow delux 10x10 and Love it!!! We actually got lucky and bought it for $80 from a guy who had only used it a few times for elk camp. After our experience with this tent, I wouldn't hesitate buying one at full price in the future if we needed to. Totally worth it if you're wanting a high quality car camping tent. Yeah spending a little extra seems like too much, but as the saying goes "Buy once, Cry once".
As I said before, we have the 10x10, so for your requirements of space, maybe their cabin model would be best for your needs? If you just slept in individual sleeping bags the 10x10 or 10x14 may be big enough. However sounds like you want to use mattresses and cots, so I don't know if the Flexbow models would be big enough.
In the 10x10 we can fit a queen blow up and 2 kids on sleeping mats with just enough space for some gear, but not a whole lot. So maybe the 10x14 Could work... Or go with a couple bunk cots?
Their cabin models are a bit more pricy, but if you buy one it will last you YEARS of quality camping!
http://www.kodiakcanvas.com/12-x-9-ft-cabin/
Or go all out and spend $1,200 on the 26x8 ground cabin!
http://www.kodiakcanvas.com/26-x-8-ft-grand-cabin-with-awning/
Here's a picture of ours while doing some tent camping last year.