I believe in fairy tales. A wedding is so special. I've attended over 100 weddings, as I used to work at a country club.
The important thing is for you to learn about the individual lives the two have led so far, to deliver that story in a touching warm and personal way and then to tell how the couple will now blend their lives into one.
Albert Einstein said, "If you want your children to be intelligent, read them fairy tales. If you want them to be more intelligent, read them more fairy tales."
True, life is not all a fairy tale, but the most beautiful moments, certainly are.
Also, practice practice practice rehearse, do not dare wing it. Know your notes. Good luck.
My first response is 39? Old souls? Sigh, I'm 49. People like hearing things about "higher power" and "personal chemistry". Perhaps talk about universal things about relationships... acknowledge that we don't live in fairy tales (especially when 39 year olds marry). I'm sure both of them have had many ups and downs in their lives but have decided that the future is happier together. I've never been married and don't attend too many weddings. I think one of the goals of a wedding is to make the audience come away with something positive in their lives regardless if they're married or not. This also has the benefit of making the reception afterwards more happy. Good luck!