Best way to capture audio at an event
You'll get the best audio by connecting directly to the board the sound guy is using. As you mentioned, the risk involved there is that you lean heavily on the sound guy and hope he doesn't screw up. 

If it's an option (depending on what kind of setup he has), sometimes he can record all the audio to a CD for you. This would almost certainly be possible if the wedding is being held in a church or similar venue with a permanent sound booth setup. If that's possible, have him record his audio to a CD (which he can give to you at the end of the day) and use the H1 elsewhere in the room.

Slight side note on this: you might also be able to get a smartphone app that lets you record in through the 3.5mm headphone jack of the phone, freeing up your H1 to use the external mics.

If you do want to keep the H1 separate from the sound board (and recording to a CD isn't an option), I'd try and find a good place in the venue to stick it. Putting it directly on your camera is an option but can be risky as it could pick up whatever noise you/your camera makes throughout the event. I usually try to keep my audio recorder/mics a slight distance from myself/camera so that I don't influence the recording at all. Sometimes it's possible to stick it very close to the bride/groom - tape it under a podium, hide it behind a bouquet, etc. It all really depends on what the actual stage setup looks like.