One way to word an invitation to an anniversary party is, "We would like to share the excitement and joy of our anniversary with you, and we invite you to join us for music, food and celebration." Wording may vary according to the formality of the anniversary party.
Wording for a simple casual invitation is, "Join us to celebrate our years of marriage with an evening of wine, food and dancing." Another casual invitation example is, "Because you are a very dear friend who has always supported us, we want you to be a part of our anniversary celebration. Let's enjoy this time together and make more memories for us to share!"
An example of a more formal invitation is, "We request the honor of your presence at our anniversary party. Please grace us with your presence and help us celebrate years of bonding and marriage." Another formal invitation example is, "Please be our honored guest at a dinner party to celebrate our marriage anniversary. We look forward to you gracing us with your presence on one of the most special occasions of our lives."
An example of an invitation written by children for their parents' anniversary is, "Please help us toast our parents on successfully completing these 25 years of marriage. You are very warmly invited!"