Usually it's the other way around! No babies/kids at the ceremony in case the make a racket... In saying that though, I have been to weddings with kids, and had kids at my own (albient ranging from 1 to about 14) and they generally get the idea that it's a big occassion and keep quiet.

I would definately go straight to the source! If the bride/groom says yes it's true then just let them know there and then you'll only be attending the ceremony...