Keep it simple, 100 BTC cold in very well hidden fireproof safe with a backup.
GPS coords of it is PGP protected.
Peace of mind

Priceless.
This sounds like the safekeeping would cost more than the worth of those coins

If its an existing safe for other unimportant stuff and you only have 100 coins fast forward year 2024, well

What if someone finds it?
I think it would be much safer to just user a BIP38 wallet and use Shamir Secret Sharing algorythm to split it into 2 of 3 pieces and distribute those to very safe places.
If someone finds one piece --> nothing can happen
If someone finds 2 or 3 pieces --> nothing can happen really, because he still needs the password and he can't bruteforce it.
So basically to steal your fund, someone needs to find 2 piece AND hit you long enough to giveup your password.
Flaw: You forget where the pieces are (you can plant more than 3 obv) or you forget the password.