Addressing Inner and Outer Envelopes -Help!

Sassenach1743

Please help me decipher the proper way to address my invitations. 

TK advises to only use first names on the outer envelope (i.e. Mr. and Mrs. John Smith, Miss Sara Jones, or Ms. Sara Jones and Mr. John Smith, etc.) and for the inner envelopes to only use titles (i.e. Mr. and Mrs. Smith, Miss Jones, Ms. Jones and Mr. Smith, etc.)

Is this really how it goes? I understand the outer envelope wording, but the inner envelope wording is what has me puzzled. I thought it was less formal on the inner envelope, like I could just write Sara and John, etc. 

What did you do? Please advise. 

Also, when children are included do I just address the outer envelope to the parents and then list the children's names on the inner envelope OR must all their names appear on the outer envelope and should it just say Mr. and Mrs. and family on the inner envelope?  

banana468

TK is correct.   If you're inviting a marrie couple it's
Outer -
Mr. and Mrs. John Smith
456 Main Street
Anytown, New York 12345

Inner -
Mr. and Mrs. Smith

If you're inviting the Higgins family and their 3 children (Emily 8yrs, Abigail 6 yrs and Travis 2 yrs) then it's:

Outer-
Mr. and Mrs. Henry Higgins
72 Cherrytree Lane
City, New York 45678

Inner-
Mr. and Mrs. Smith
Emily, Abigail and Travis

People should be addressed with titles as you're addressing based on the formality of the event and not your relationship.   If titles are used on the outer then they need to be used on the inner.