It's interesting that the president of an art association would present you with this issue without a specific request for a remedy. He surely knows that replacement would not be possible had he damaged a pastel or oil painting. Had he purchased a photograph by an artist who is deceased, he would also realize that there would have to be a possibly significant fee paid to repair a damaged 'graph if it were even possible. I wonder if he fully realizes that you've sold him a hand made print, and not an inkjet-pushbutton "poster". It's an interesting quandary that purchasers may expect remedies to damaged work in direct proportion to what they think may be involved in making the remedy.
I think, though, that you've gotten a preponderance of suggestions that speak to accommodation and building good will...especially in your own local region. I think that advise is wise. I hope you'll get back to us with the results of your conversation with the guy.