What bike (carrying) racks are available for Pop-Up Campers?
Add a second towball on the rear of the camper and fit a car bike rack for three bikes.    If your camper has a spare wheel here, then a wheel mount may also work.


Add another upstand of some description on the front of the camper for a duplicate setup, and put three bikes on the drawbar.  Noseweight should be about the same.
 or


Similar option is to run two towballs on the towing vehicle, like this


The other option is to put some bikes inside the camper before folding it, but there's often not a lot of space once its all folded down.