I'm sorry!
I guess I just don't see the need for secrecy, which was a big component in this thread where people had to promise not to tell, no one knew, etc. I don't see why a wedding in this case can't be what it is: a vow renewal rather than a marriage ceremony. I think the dishonesty isn't necessary. I really don't think anyone would treat it any differently, and if they do then don't invite them. Only someone small would resent someone else being happy and having a celebration of their love. (And wouldn't wish upon anyone what happened to the couple I know. What a memory of your wedding day!)
The invites could read, "Jack and Jill were legally joined on September 1, 2007. Now they're ready to share their joy with the world. Please join them for a public reaffirmation of their vows on...."
What ever you (and everyone else in this thread does) I wish you luck and happiness!