Our daughters have been camping since they were 5 months old. They began sleeping on one of the couches with the pillows fitted to make a "well" for them to sleep in. When they began moving around, the Pack-n-play would go in the space where the table was removed.
When they were about 18 months old, they began sleeping in a toddler bed at home, so the transition in the camper was easy. DH configured a spider net that was attached at the bottom, but was velcroed at the top for easy access. This also kept them in the bed during the night - we had to assist with getting them out to go to the bathroom or whatever. They slept in there until they were about 4, then got to graduate to the top bunk, which also had bed rails.
Now they both sleep on the bottom bunks because it's too much of a pain to crawl up and down to go to the bathroom. They couldn't wait to get up there, but now, they both want the bottom.
2017 Ford F350 Crew Cab 6.7L 4x4 DRW