Beautifully written and presented, Michael. Took me back to my childhood picking through rocks and pebbles, looking for… don’t remember. Fossils and shell imprints seems likely, though.
Suggestion? Find a nice bag, cloth with a drawstring or whatever, and have him put the “best” rocks (he’ll know which) in. Then print out your word snapshot and add it to the bag. Put the bag in that place y’all save stuff that gets saved because you aren’t throwing it out, just yet. In a couple decades it’ll pay off. Or be opened again with the words, “Hey, want to see something your grandpa wrote when I was your age?”