Aim for 34 weeks prior to an event when sending out an invitation letter maybe more if it's a major event that requires tickets or an RSVP. I hope this letter finds you well.A good church invitation letter should be warm, welcoming, and to the point. The document is an invitation letter from the choir group "Himig San Antonio" inviting the recipient to their 10th anniversary thanksgiving concert. For a marriage in a Church other than a Catholic.