Put them inside.
You can also have someone install a 2" receiver on the front hitch, it is REALLY strong, and then mount the bike rack there, in front of the trailer. Once un-hitched, you can pull the truck forward, with tailgate down, but close to the RV. Then lift each bike into the truck bed, and then move the truck forward enough (or park it) and unload the bikes from the truck.
The rear bumper mount will work, and you have to make sure that the RV is able to attach the frame mounted hitch and rack to that hitch.
Fred.