I don't think it really matters. But in society today you normally say Mr. then Mrs. I would do that to be safe.
Mr. used to be acceptable to address a household by just using the last name, e.g. "Mr. Jones". In modern times, it is typically to use "Mr. and Mrs. Jones" or "Mr. and Mrs. Timothy Jones".
Mr. and Mrs. (ex. "Hello, Mr. and Mrs. Evans" instead of "Hello, Mrs. and Mr. Evans")
They are two people - two is plural, so it should be "Where are Mr and Mrs Jones?"
Pan and pani
Frau = Mrs.Herr = Mr.