I've been on a "team building" hike that turned into a poorly planned overnighter. as in the leader had planned on us being out over night, forgot to count sleeping bags, check weather, bring food. there were about 30 of us, half guys, half gals, and I can tell you there were a couple of ladies very unhappy spending a night without spare...sanitaries... and a few folks with no contact lens cases or saline. Since then I've gotten more careful about what I pack (I had about the only pack and it was mostly first aid, just a little waist pack) I also lost a lot of trust for that particular team leader, and made working with him that much harder.
point is, if you make it uncomfortable, and miserable, you won't gain any friends, if it goes ok, people will be ready to learn how to make it better and have more fun. I'd say do a "grab and go" like 1066 said, and go over what people had, hike a bit, set up camp, critique, come home. Then once people have had a chance to fix/ replace gear (if an expensive pack ends up not fitting, it could take time to replace) then do the real deal, but have a "backup" stash and use an area you know, (don't have to guide, maybe be "injured") so that the variables are minimized. Better learning that way IMHO
personally I could "bail" with my EDC pack, but it wouldn't be pleasant at all, and even 10 min to swap packs and pack the extras would be enough to make it "fun"