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.
[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.