Learning braille. You can learn it yourself and then teach it to him using paper braille books. It's very rewarding, he'll be able to read, and you'll be able to read in the dark.

Win/win/win. Since he's just starting out try Unified English Braille instead of EBAE (old version). Here's a course for you if you're sighted: http://uebonline.org/

Also, try to teach him how to use a screen reader for iOS, Android, macOS, Windows, ect. before it's too late. Assistive technology is really baller. He doesn't want to miss out.

Instead of focusing on new hobbies figure out how to make the hobbies he already likes accessible.

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Is he retiring from his job because he is blind and doesn't think he can do it anymore? If he wants to learn Braille himself Hadley is the best resorce.
https://www.hadley.edu/braillecourses.asp

he could get into music! playing some instruments can be easy enough without vision, unless you're trying to play songs by sheet music instead of by ear. singing is even easier to do without sight, and finding new music can be a hobby of it's own! for finding music, it generally is necessary to use accessibility programs that either are built into a computer, or can be downloaded. certain sites are more compatible with accessibility programs than others, so that's something to be aware of.

When you said "old-fashioned" I immediately thought of knitting. I knit by sight, but it's tactile enough that I know you can knit purely by touch as well, especially with bulkier yarns.