Since it's not going to be a religious ceremony, this is how the ring exchange will go. I don't know how you do the wording on the contract- if you have a specific layout you use- but if you don't, I would absolutely love to see some elements of this phrased into it.
Sumerian Cloisonné Ring, Iraq, ca. 3000 BCE. (Louvre Paris Reunion des Musees National/Art Resource, New York/Photograph by Zeva Oelbaum). Possibly a wedding ring. *Cloisonné is an ancient technique for decorating metalwork objects, in recent centuries using porcelain enamel, and in older periods also inlays of cut gemstones, glass and other materials.