if you have an iphone, rvparky is a free app which will help you land for the night.
GS Camping ( as in Good Sam) and KOA are useful apps too.
mid sept is still hot in PHX, so we are all up in the high country- esp weekends. try to do the GC mid-week.
be flexible
Vegas: Ballys has easy parking for RV's on the East side of the building enter off of East Bound Flamingo 1st driveway AFTER the light by the sports book and food court.
look at google maps satellite view, you'll see it
or there are a couple of RV parks South about 5 miles ( around silverton) ...under the flight path at maccarran- I have not stayed at any of them
Mike