Surprise wedding: Engagement party and Wedding in One

We're having a nice surprise party wedding next week. The couple have asked their friends and family to dinner to celebrate their engagement, and then I'm going to make an appearance after the cocktails, and ask the couple to come forward -- and we'll have a wedding, instead of just a party. Only two people are in on the plan, and it should be a wonderful family event. The ceremony will be simple, they have bought a simple pair of rings, and we'll be sure to have a camera ready.

We've done this before, and it's always wonderful. Get your license a few days ahead, have a plan for pictures, a special dessert, glasses for toasting, and lots of hugs. They are going to ask their mothers to hold their rings, after they announce the plan, and their sibling/dad will sign the license. I think it will be memorable.