Unless all family-members and potential heirs are fully adept at self-custody, strongly recommend paying for a collaborative custody service (until better solutions develop).

If you’re dead set on DIY without an outside third-party, consider a “poor man’s miltisig” (wallet with passphrase, a sort of 2-of-2 multisig). Because properly setting up, maintaining, and later reconstituting a multisig wallet are difficult and can lead to catestrophic loss.

POV: I’m an experienced probate lawyer and executor