My two friends and I are going to spend quite a bit of time preparing a mega-game. It will be a weekend long gaming session with around 20 players, and the three of us as GMs. We are trying to figure out the best possible use of GM resources given the large number of players. Should we reach out for 'helpers' who aren't quite GMs but do some housekeeping tasks? If that option does not exist, what other methods could be used to keep the game running smoothly?

Good answers should pull from experience running large scale games with multiple GMs, and what techniques were used in managing so many players while keeping all of them engaged.