Congrats to the couple! How very exciting.
Sir and I are getting married soon as well, and we plan to incorporate some kink into a small party for friends from the local community just before we leave for the actual wedding. Kind of a cross between a second bachelor/bachelorette party and a shower. A friend had a similar event and we all purchased toys to give to the couple and then broke them out at the party. For example a few of us went in a really nice new whip, and since the groom-to-be wasn't very experienced with a whip another member taught him how to use it and demonstrated on the bride-to-be. Also Sir and I plan to write a set of vows for that event and have a collaring ceremony.
We aren't planning on working anything into our actual ceremony but we wanted to celebrate all aspects of our life together and find ways to honor all of them, and do so with the people who support us in those parts of our life.
Good luck with the wedding planning, I'd love to know what you end up doing. Wish you both all the happiness - kuri