Take whichever camera that is light weight, unobtrusive, quiet, and non-threatening to the hired photog. Then keep an eye on the hired man(discretely)and take mental notes of what he does, so that later on you might feel up to shooting a wedding yourself. You can ask questions, but be aware of the tone of the response(some of these people are primadonas)and by all means do not shadow them. Stay alert, you may end up with the better shots, and find out you are a good wedding photographer.

Rick