It is very difficult to leave coin to multiple heirs without relying on some kind of trust of someone.

For many people, you should have a single seed that can derive all your private keys that can spend all your coin. You should have your seed stored in a location (or locations) your heirs cannot easily access while you are alive but would be able to access upon your death (such as a safety deposit box), along with instructions as to what to do with the seed to access the coin.

If for some reason you need to have multiple seeds (such as one for what you spend with your phone while out, or one for cold storage), you can repeat the above process for each seed that controls any of your coin you wish to pass onto their heirs.