Not sure what the right answer is for you, but here are some thoughts...
Its tough to run a full size RV AC unit without having a generator. It would take a very large battery pack to run it for any significant time. It gets to the point where you would need to consider Lithium batteries for there energy storage density.
If you want to have a look at whats involved in running an RV AC off batteries, go to FitRV.com and search it for their post on running AC off batteries -- be prepared for some sticker shock.
Generators are also tough to install in a PM -- it seems like about the only practical place to put them is where the spare tire goes, and that means mounting the spare on the rear doors or something like that. Generators are also disliked (and that's a mild word) by other campers. In a lot of places people with generators are exiled to a special place where they can share the noise with others with generators. I actually saw a minor fist fight break out between a generator owner and his next door neighbor in the campground at the Aspen Bells in CO.
If you insulate the PM well, you can get the heat gain down considerably from what it would be in a regular RV, and you might be able to use a smaller AC that would not require a generator to run -- although it would still require increasing battery bank size.
Some places you might look at for a smaller AC:
Climate Right http://www.climaterightair.com/
(they sell ACs for Tear Drop Trailers)
Small room AC: https://www.amazon.com/Frigidaire-FF...=small+room+ac
This is a 5000 BTU/hr small room AC -- its pretty efficient as small ACs go, and dirt cheap.
But, you have to figure out how to mount it. I have seen articles on people using this AC in RV's -- google around for it.
To give the two fan approach a good chance of working, important to insulate well, and to have good reflective shades on the windows -- making them with Reflectex works well and is cheap and easy. This is what we did:
The heat gain through a window in the sun can be over 200 BTU/hr per sqft of window -- has to be controlled or you will never get there with fans only.
We use one MaxxFan coupled with open windows, and this works well for moderate temps -- some tests on my van here: http://www.buildagreenrv.com/keeping...n-cool-a-test/
Of course, parking the the shade makes a huge difference.
If you are traveling in a dry area (low relative humidity), then an evaporative cooler can work well and is MUCH more energy efficient than a conventional AC.
RD has a post on one he did that is really clever and simple, and works in conjunction with a roof fan.
Scroll down this page a little for plans for several more DIY evap coolers -- one is for a small trailer: http://www.builditsolar.com/Projects...htm#ActiveVent
edit: should have mentioned that if you camp at places that offer shore power, the AC is, of course, a lot easier. If you go that way, you might look into a hybrid inverter, which will let your batteries help a not so good source of shore power.