I am a member of a family where the anglo-saxon naming tradition is not often followed. So here are my rules...

Husband and wife with different last names..both first and last names.

Husband and wife with different last names and children..."The Family Jones"...

If I only know one of the spouses well...to the spouse I know.

If I do not know them well enough to know how I should address them...do I know them well enough to send a card????