This is one of those cases in which you need to know the options your bank provides, lay them out and let the customers decide what best fits their situation. I don't recommend that you steer them one way or another, since the choices they make can affect what happens when one or both of them die.
You can explain the mechanics -- a power of attorney ceases to be effective on the death of the individual who grants it. An authorized signer's authority to sign on the account also ends with the death of the individual who authorizes it. Adding the children as joint owners could have tax implications.
If the customers don't know which route is the best for them, they should consult an attorney for guidance. You should not try to fill that role.
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John S. Burnett
BankersOnline.com
Fighting for Compliance since 1976
Bankers' Threads User #8