Invitation to a surprise party for a person's birthday / anniversary / celebration.
We cordially invite you to celebrate echo $NAME; ?>’s [Number]th [Birthday / Anniversary.] Shhh…. it is going to be a surprise party!
[NAME] and [Name] have been happily married [and raised a family of [x] kids] for [number] years. They promised to love and cherish each other for the rest of their lives. As their dear friends, we are part of their incredible journey with them and help them to celebrate their commitments to each other again.]