Lets start with giving this couple fictional names to protect the innocent and the guilty:
Husband = John Smith, Wife = Jane Smith
They are a traditional couple (Not offended by Mr & Mrs John Smith titles and the like)
OK here’s the situation.
I work with John Smith
Jane Smiths Mother died recently (I have never met her mother). I have only seen Jane maybe 2 times, perhaps 3.
How should I address the card (the name(s) on the envelope) and the name(s) in the card.