We have a bike rack on the back of our 5th wheel camper. It fits into the hitch. The rack has a locking hitch pin. I have a chain thats in a rubber sleeve and a cable that I use to lock all the bikes togeather. When I stay over night, with the bikes on the rack, I cover it with a blue tarp. When the bikes are off the rack (at the camp ground) I use both cables to secure the bikes to the camper bumper (and use a blue tarp.

I would be a little worried if the bike rack didn't lock to the car. Either get three long cables and lock everything togeather (and park in a well lighted area next to the from desk) as much as possible or take the bikes to your room.