I think that Hps4evr and Tubby89 have some VERY good ideas there. I wasn't able to attend this year's 101 (stupid job...interferes with my wheeling WAY too much), but from what I saw participating in last year's run, they're right on the money. I know that if I had been offered the chance to keep participating on Sunday when took the 101, I would have been all over it.
The other suggestion that I would make:
#1. Smaller groups for the trail runs after the gravel pit, and different routes for the groups.
#2. If possible, assign volunteers to specific tasks early, and use some of your most experienced volunteers in a "swing" capacity...they can cover for those folks that have last-minute breakdowns, or help out in places where things are slowing down. IIRC, you spent a bit of time in the military, right? Maybe think of using them as a "Swing NCO" for the course.
#3. Part of the "meet and greet" can be questionnaire that asks folks about their wheeling experience. If you break them into groups, you can choose trails well suited to expereince levels.
The Sunday time could include a quick tutorial on winching/recovery as well.