Audesapere, wrote "you are marrying a non-believer"
Maybe you didn't read that he was studying to be a minister, and is gonna use scripture in the wedding ceremony. I think he's a believer.
Seems the wedding is there because HE wants it in the church. If that's not a big deal, then have it somewhere other than the Chapel, and get the people you invited to show up. Problem solved. He can still use the scripture anywhere you have the wedding, and most scripture is the same or similar among all the versions, so the JW's can relate to it too.
What would be funny though is if he whipped out a big Cross in his hand near the end and waved it around like they were vampires or something!! Ha Ha!