Is it actually possible to secure your coins while also allowing access to "near and dear" when you die?
This is what safe deposit boxes are for.  Write your passphrase on a piece of paper and put it in a safe deposit box at a bank that will allow only you (with proper identification) to access the safe deposit box, until you die, whereupon access will be available to whoever you've designated through proper legal documents.
If you are worried that some bank employee will break into the safe deposit boxes, then put half your passphrase in a box at one bank and the other half in a box at a different bank.
I'm sure you can imagine ways this can still go wrong, but unless I'm missing something, they are all extremely unlikely.