[header] How to address wedding invitations to a family [title] Decide whether to do double-envelopes. [step] If you are planning a more informal affair, it's okay to go with just one outer envelope. That way your invitees with open the envelope and see your invitation right away. 
If you prefer formality and tradition, opt for the double-envelope method. This means that your invitees will need to open two separate envelopes before seeing the event details.