To sum it all up:

Gold or not the credit card shown to the agent or on file at rental pick up HAS to be IN THE NAME of the primary driver.

The primary driver MUST be present at pick up.

So the only way to have your daughter or son in law pick up a car is to reserve a car in one of their names with his or her credit card respectively.

Upon RETURN, you can switch cards for billing so that the charge is billed to your own card if you wish. Indeed at the HLE where I'm talking to an agent at each return, they always ask me if I want to leave it on the same card.

Also you or any others arriving later won't be able to be an additional driver on the car they pick up unless they come back to Hertz when you arrive and you (and/or others) are added to their rental record.

Worth noting that the primary driver needn't necessarily be present for return, although I'm not sure if the card switch would work if they aren't. I have had an additional driver drop a car off before though.