The laws of each State are different. This is true in other countries.
I suggest you consult a local attorney at law in your jurisdiction, with a knowledge of Intellectual Property law.
I suspect you MAY be looking for a "durable" power of attorney. (That means the power of attorney survives your death.) The power would instruct the person you chose "At the time of my death, please do X, Y and Z." Then the power dies, and is of no further effect.
If there are huge financial implications, you might consider having the holder of the power post a bond to insure full performance.
But please, get a professional to help with this. I don't try and fix my computer, because.... well.... I'm clueless. As far as I'm concerned it's all magic and that's the end of it. It took me three tries to get this posted, how's that for clueless?
Just my humble opinion.