Book Idea
I have a book called, Show Me! Devotions For Leaders to Teach Kids, by Susan Lingo, published by Group. This is a book of science-based devotions that I have used several times.
It has two possibilities in it you could use. One called "The Amazing Water to Wine Trick", and another called "Changed Forever".
They also suggest that you show the kids how the trick was done, so they can go home and share it with their family!!