Our twin grandchildren (boy/girl) live with us. They are almost 2 1/2. We moved them to toddler beds when they were 18 months old. Girl twin had climbed out twice, once safely and once with a big thump.
Their door is closed during naptimes and their room is completely baby-proofed. At first, there was a lot of getting up, playing, etc. We would find them after nap and in the morning in the same bed, in each other's beds, etc. They each had once experience of falling asleep on the floor and then the novelty of being able to run around wore off. They have books and most of their toys to play with. However, they have always been good nappers and sleepers and stay in their beds to fall asleep. When they wake up they will sometimes get up and play, read a book, talk to each other.
With our own children, once they began fighting sleep during naptime we changed it to "rest time". It was understood that they would go to their room and have quiet rest time. They were allowed to read or play quietly, which almost always led to falling asleep for a nap. They continued this practice through kindergarten.
As long as you don't insist on sleeping during naptime and don't make it an issue, they will usually sleep if they need to. The only thing you have to insist on is quiet.