I echo what Lisa just said.
I'd also add - if only the wedding couple and maybe one or two others have any experience of contra dancing, I would definitely NOT do a "regular" duple minor contra; I would not teach swings; I would not use any confusing figures that you wouldn't use for a family dance that's a ONS. Don't "build up to" any contras or anything other than keeping it simple and fun. They're not there to learn. DON'T make the dances long (it's not like a monthly contra dance).
They're not there to dance; they're there to celebrate the wedding; I agree that you charge extra if there will be alcohol; and if they tell you that you have an hour, figure you may have 20-30 minutes (unless you come after people have had time to drink a bunch - in which case you may have 2-3 dances at best) and you want to pick the most fun, most easily accessible dances that barely need a walk-through.
Doing a spiral at some point (making sure the wedding couple is who you are holding hands with) is a nice way for those who participate to honor them (when you and they get to the center).
If your main reason is to recruit new dancers, I would not do weddings.
My 3 cents - from both experience as well as having read a ton of callers' remarks and advice about calling for weddings.
PatriciaPatricia Campbell
Newtown, CT
Celebrating Community Through Traditional Dance and Music