I would tell them to avoid buses at all costs.
I'm not sure they need to keep using your account as they could replace your AdSense code with a new account.
More important in my mind would be the transfer of the domain names and such.
This is another reason why I have my main money making web site domains prepaid for 10 years in advance so whoever is left won't need to worry about some things for a while.
Plus, I don't have to worry about the vultures camping on my domain just hoping it will expire ;)