A.M.
It's not a keepsake, but there's a beautiful (and very popular) hardbound book out there right now called the Dangerous Book for Boys -which is like how to build a treehouse,etc. It's aimed at "boys from 8 to 80" so it'd be for him and for helping to raise them and you could inscribe it with something really special. Actually it's been so popular they did a girl's version. It's a totally different way to go if he's that kind of guy...