I would probably recommend try to add /sethome for the players in the Parkour. so that way players can set there home and come back to the same spot but..For them to get back up your gonna have to use command blocks at the bottom of the parkour (where they fall) that say "/home @p" with pressure plates on top of them so players can step on the plates and they come back to there last spot. But other then that, That's all I know pretty much. I don't know if there is plugins for it but, yeah.