Seating chart

OK, silly question about a seating chart. Here's the deal:
We are having a few very long tables for the reception, and so we are assigning actual seats. I am making up a chart to at least tell people which table to go to. I am listing the guests in alphabetical order, but have a question: I am obviously doing it by last name, but should I do it for first names too? Like, if someone's first name starts with the letter A, but their spouse's starts with M, should I list them together, or put the person whose name starts with F between them?

Do you have to list them separately?

Or can you just put Mr. and Mrs. John Doe?
Or Mr. John Doe and Guest

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Posted by sarahradio5

Do you have to list them separately?

Or can you just put Mr. and Mrs. John Doe?
Or Mr. John Doe and Guest

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We're not using Mr. and Mrs. since the reception is pretty casua.