Having worked many years in retail store management, I can tell you that this "just offer" approach is a good way to make people hate these alternate exchanges if you don't first make it really clear that they can't just put it in the bank deposit with the FRNotes.
I've heard people brag about this approach and I'm certain they are leaving a trail of unhappy, disappointed, annoyed and disgusted people behind them who, in some cases, probably toss the coins in the trash....no matter how delighted they were when you handed it to them.
You have to be sure they know what they are getting. Some people will prefer (gasp) FRNotes. Foolish, I know.
What would be fun and educational is to go back the next day and see if you can get them to trade them back again.
What do you think? http://consequeries.com/