Upload & Sell: Off
I'm setting up on the side of their walking path, just need to plan a spot that has the sunlight to the rear. They'll step just off of the path, smile, I'll take the shot, they go back on the path, etc. Teams won't all be 10, probably mostly 4-6 with as few as 2 and as many as 10.
The likelihood of a tent is slim. I'd be happy to use such a shelter from the sunlight if it were available but after scouting the location, taking test shots in the same sunlight, and discussing the shoot with the event coordinator I have to plan on no shade and 11am.
I'm happy to offer my services to them for free but since it is not a paid gig I can't see the point in spending the money on a dual AB1600/Einstein setup. I'm simply looking to take the best possible photographs with what I've got on hand...very unGAS-like, I know
As far as flash position goes: 580 on camera/direct or bounced out of an umbrella at subject eye level and 45 degrees?