One of the most frequent questions I get from couples who are getting married and want me to address their envelopes, is simply, “How?” People don’t know when to use Miss or Ms. or who to include on the envelopes. For most people, a wedding is the first big event in their lives where they are mailing out a large amount of envelopes, and it isn’t like people study up on Emily Post anymore. This is information about the ‘proper’ way to address envelopes (mostly takes from The Wedding Invitation Handbook, Julie Holcomb), with some pretty pictures as examples. In every situation where you are hosting an event, people just want to know what they are supposed to do. No one wants to show up to your wedding with a date to find out that there is no seat for their guest, or bring their children along to realize that it is a no-kids-allowed party. Addressing envelopes is a way to make it explicitly clear who is invited to your wedding. Of course, it is 2015, so if you want to bend the rules a bit, there is no invitation police who will come knocking on your door if you want to use nick-names on inner envelopes, which I think is a very sweet idea!
Outer vs. Inner An outer envelope has the address on it, and is addressed to a couple or an individual. An inner envelope is addressed more personally, which denotes exactly who is invited. For example, if an inner envelope has a couples name on it, but no childrens names, it should be clear that the children are not invited. If you choose to not use an inner envelope, then the outer envelope should name who is invited.
Inviting Children Children over the age of 13 or so should be sent their own invitations if possible. When a child is invited to a wedding, his or her parents are listed on the outer envelope, and the child(rens) names are listed on the inner envelope. It is generally accepted that children are listed by first name only, and in order of oldest to youngest. If your event is very formal, the title of Master may be used for boys under the age of nine, as well as Miss for young women. If there are two brothers, The Masters may be used – for example, The Masters Anderson. For more than one young woman at one address, The Misses may be used. Of course, if you are having a less formal event, or only using outer envelopes, a simple ‘and family’ or ‘The Smith Family’ will suffice. 
Here is a chart I put together of likely guests and how they should be addressed. You can download it here: Everly Calligraphy How to Address an Envelope
Or see it here:
(Click on the image to make it larger if needed)
Hope this helps with your addressing needs!! xo Charmaine
everlycalligraphyblog 