Our Adventurer 910FBS was purchased w/o a genny....but with a compartment for one.
We had experience with an on board Onan in a previous camper, and did not enjoy the noise and vibrations.
This time we chose a portable Yamaha 2000 generator. The Honda is a very nice unit also, but I've had great luck with the Yamaha genny's in other situations, so I chose Brand Blue. It will run the A/C in the 910FBS without complaint.
Our truck, being a gasser V10, is used as the extra fuel reservoir (if need be) by accessing the main fuel tank with a simple foot valve style siphon hose. Generators of this size get great fuel "mileage" though, so this is hardly a real issue.
In truth, we very, very rarely use a generator at all. Our camper has all LED lighting, plus I'm using two 6v golf cart batteries (they'll fit in the Adventurer's battery box...barely!). We've gone 4 nights in a row, 2 showers/night & with the heater going on regularly....with no power issues. In fact the only reason we haven't gone longer than that was that the grey tank fills up after 8 showers, so we have to move to dump. Since we're normally boondocking, the drive to a dump station will charge us back up.
But just in case....we do keep the Yamaha 2000 with us.