It is traditional to use a complete, formal name and address. Do not use any abbreviations except: Mr., Mrs., Ms. Dr. or Jr.
All Names should be completely spelled out such as:
Mr. and Mrs. Gerald Andrew Klein
(instead of Mr. and Mrs. Gerald A. Klein)
If you know the full middle name, you can use it, if not, do not use initials, simply omit it
First names (without Mr., Mrs., etc.) or the phrase "and family" are not proper except for informal weddings
For Married Couples
Outer envelope
"Mr. and Mrs. Gerald Klein"
Traditionally, the husband's name goes first, unless his wife happens to have a professional title, in which case she should be addressed before him.
When addressing a married couple, always address both members of the married couple, even though you may only know one or know that only one will attend.
Married Couples (different last names)
Outer envelope:
Mr. Dean Forrester and Mrs. Allison Smith
Outer envelope (hyphenated name):
Mrs. Allison Smith-Forrester and Mr. Dean Forrester
Married Couples (with professional titles)
Outer envelope (male professional):
Doctor and Mrs. John Jones
Inner envelope: Dr. and Mrs. Jones
Outer envelope (male judge):
The Honorable and Mrs. Mark Darcy
Inner envelope:
Judge and Mrs. Darcy
Outer envelope (female married judge):
The Honorable Elizabeth Darcy and Mr. Mark Darcy
Inner Envelope:
Judge and Mr. Darcy
Outer envelope (male officer):
Colonel and Mrs. Bruce Reynolds
Outer envelope (female officer):
Lieutenant Bella Wayne, US Navy and Mr. Ryan Wayne
Outer envelope (both professionals):
Doctors John and Bridget Jones
Outer envelope (two professionals different professions):
Doctor John Jones and Reverend Bridget Jones
Married Couple with children
Outer envelope: Mr. and Mrs. Riley
Inner envelope: James and Sarah
Susie, Johnny, and Meg (list by age, oldest first)