If you are thinking ahead, I would probably write some kind of severance into the contract that specifies that it's if the contract ends due to either the death or a move to nursing home kind of situation. I wouldn't leave the money in the will, because that's going to leave a long period before they receive it, and many people working caregiving roles, even at above market rate, aren't going to need money in the aftermath of a sudden job loss.
I think, although I could be wrong, that writing it in the contract would mean you could just issue a final paycheck without waiting for the estate.