I spoke with one of our pastors today and he assured me not to worry. He said that unless the church asks them to completely cut off ties with our church, they should be able to officiate the ceremony. He said to think of it in the terms of something that would happen if they were sick the day of our wedding. That made me feel a lot better!
Unfortunately, I won't know for sure if they can officiate until Sunday when we have our congregation meeting.
Fingers crossed this all works out.