One suggestion, keep them in a separate fireproof safe and LEAVE THE KEY IN IT. My parents had all their papers in a small safe, and burglars broke in, couldn't open it, and took the whole safe. Later the police found it open in the local reservoir, all the papers ruined. Had the key been in it they would never have bothered to take it. It will also save your family from looking for the key.
Might as well put them in a dresser drawer with a sign saying “Keep Out.”