I've been down this road several times and learned the hard way. I do carry our bikes on a receiver at the back of the 5er. They get bounced around a lot back there so a good rack is required.
I started out with the kids bikes when they were small, had a "heavy duty" 4 bike rack from walmart, carried 3 bikes on it, had to remove one of the bikes 2 hours into our first trip and put it inside the 5er as the rack bent.
Then I got a really "heavy duty" rack from Cabelas. The main post on it was huge and it even had a hitch adapter for pulling a small trailer. No way that one is going to bend! WRONG! It did make it on a 1,100 mile trip, but was noticeably bent. Time to try something else.
They say you get what you pay for. Well I paid for this rack..
https://www.etrailer.com/Hitch-Bike-...S-9036XTS.html It is the only one I've found that holds up to the abuse of hanging 3 or 4 bikes off the back end of a 40' 5th wheel.
I also have a smaller, little bit lighter, 2 bike rack that I use for the DW and my bikes. We normally use that one on a front receiver hitch off the front bumper. I used it on the back of the 5er a couple times. It held up okay, but I did find a weak point. There was a small pin at the pivot point that locked it into place. I snapped the pin on one trip. Had to replace it with a good quality grade 8 bolt.
If you can find or have someone build a pin box rack, it's probably a better way to go, but then you have to watch that close when turning, especially if you have a 6' bed. The rack I linked above will work, but it's not cheap.