It's funny, I have never stayed at a KOA before, but next month (Oct 2016) I will be at the KOA in Petaluma, CA for a couple nights and then in Feb 2017 we will be at the KOA in Tucson, AZ for about 10 days.
http://koa.com/campgrounds/tucson-lazydays/
Looks like a "resort" KOA.
The drive from here to there is about 18 hours so we will have to do at least one overnight, maybe two. I don't like to drive more than 8 hours per day over multiple days. Maybe somewhere near Modesto and then in Banning. Our son lives near Los Angeles, but not anywhere we could bring a trailer and I don't really want to deal with that kind of traffic with a trailer, so we will skirt the area via Bakersfield - Tehachapi - Hesperia to Riverside.
I've never been to AZ on vacation (I've been through and I have been to Phoenix for work), so we will see what it is like.