For high reliability, I think I would suggest engraving it into a low reactivity nonvaluable metal, perhaps titanium sheet would be a good choice. Couple that with a backup on printed archival paper using carbon toner or an art-grade ink or dye. Between the two of them they will probably resist damage for 100 years or so.

Brass or bronze would also be a decent option, but you'd have to make the text larger for it to be readable with corrosion. Perhaps braille would be an interesting choice there.

And ceramics are a great choice - clay tablets, when fired, can last millenia.

I think between the three of a metal sheet, clay tablet, and paper book, one of the three is almost certain to survive a century.

the question is more about making the content readable by his progeny. Otherwise, encode into bitcoin ledger, done.