I think someone's already mentioned this...but its worth repeating-
Be extra careful giving people any medication they could have a reaction to. One time in my high school band there was an issue because someone gave someone else medicine after they sprained something. The issue was with a school policy, which is different of course, but I don't know what legal muck you could get into if someone has a bad reaction.
Really, the likelihood of trouble with this...probably none. Best to be on the safe side though. I think its a cool idea, by the way.