I'd stick with one film and one camera. Even low-key weddings get hectic and it's so easy to mix up films/cameras and then you may end up rating a film wrong or even shoot B&W when you think it's colour - a disaster!

I'd use the F6 with Pro 400H. If you really must lug around more than that, perhaps a Leica with fast B&W (loaded beforehand so as not to get confused). Keep your spare films in your right pocket and transfer to your left pocket when done.