1 You can't use \include inside a file which is read by \include. 2  This is by intention and is because to avoid issues with the .aux files. 3  Otherwise three .aux files (main, parent \include, child \include) would be open at the same time which was deemed to complicated I guess.
Timing the Invitations. It is customary to mail your wedding invitations about eight weeks before your wedding date. If you have already mailed your save-the-date cards, then your wedding guests will be expecting your actual wedding invitations in the mail. The process of choosing your wedding invitations and preparing them to be sent out can be time-consuming so it is important to not procrastinate and allow yourself plenty of time.
More important, though, is the simple courtesy of responding to someone who was nice enough to invite you, even if it is to say that you regret that you will not be able to attend. Many wedding invitations come with a response card that you can mail back right away. Other written invitations will carry the host's telephone number so you can call with your reply, although under strict etiquette rules, a written invitation requires a written reply.