Close the marital account. Open a joint account for the mother and son if that's what they want.
My experience as a trust officer involved doing almost nothing but settling estates for 5 years. It's important to be solicitous of a surviving spouse's feelings, but not so much that you start cobbling solutions together.
While it may seem that banks are being courteous in this situation, things ultimately have to be done correctly at some point. It's no less painful for that surviving spouse when they "get around to it" some years later - they are forced to relive the event again at that time.
You make it easier on them by doing things right and in a timely manner.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.