Make sure you get the coaches to create their own (pulled, pushed & up-to-date) forks of the undergound repo before the event, so that learners can fork from them and then PR back which can finally be submitted back to the main repo 
It can be
A) handy to show url’s of the coaches repos so learners can grab one easily (or distribute them another way you like best)
B) Great to show the commit log of the main repo (on a projector, etc?) to see it updating as the workshop goes on!