I do training rides similar to that distance all the time on a compact, and very aggressive road bike, 50cm + 7cm of seat mast, with a saddle to bar drop of several cm, I ride relatively slow, simply for endurance and fatburn.

You shouldn't have much of a problem, especially if the bike is carbon [didn't check] My bike is Aluminum with a Steel Seat Post, and a Carbon Fork and I'm very comfortable after a long ride on it, just keep your hands on the hoods, or on the flat section and you'll be fine. And keep a high cadence... And remember that while they are new, they all know how to ride a bike, I'm sure they have some sort of fitness, and they are probably a bunch of immature idiots who will try to be Lance Armstrong on a hybrid, so the pace will be a little faster than you anticipate, at least on the first day.

Don't adjust anything other than maybe your bar height. Honestly you'll screw up your knees if you adjust your seat higher or lower.