I've browsed through a few threads like this one, where the OP seems surprised, if not afraid, when asked by a client for a digital copy rather than a print.
Replies from fellow photographers on this forum tend to generally advise to "run away" or tell the client "my way or the highway".
Why are you guys that afraid?? It's only natural for people to ask for a digital copy of photos, simply because that's how most people consume them nowadays. They want to post the photo on their FaceBook wall, mail it to aunt Betty, set it up as wallpaper on they computer, carry their photo album with them anywhere they go with their iPhone/iPad. People use digital photo frames as well.
The guy stating he wants a picture for non-commercial, non-promotional use, is merely saying he just wants a picture of his son for himself, not to make profit on it or undercut the photographer by selling it around. He just want a fair price that's all.
When I've done my wedding photo shoot, I insisted to get a copy of all the pictures that were also printed in the albums. I paid for that, and got full resolution pictures. I didn't make a single print of these. But I sent them by email to friends and family leaving far away, posted some on my website, used others as wallpaper, etc. So relax guys, your income isn't under treat because your client would like digital copies.