To me the extra 2'-4' is no big deal. It will be that jump from 19' to 28'-32' that you will have to get used to. I would strongly recommend a WD hitch as well going to that size. I have almost the same truck as you but its a 2012 and no air suspension. I use a WD hitch with my 19' toy hauler and when loaded up the trailer is about 8500 lbs. I have never had any sway problems but never tried to tow it without the WD hitch either.
As far as camp spots... from my experience some (not all) primitive campgrounds will be the place with a 25' and under length restriction but most RV parks are set to handle trailers all the way up to 40'.
