I did weddings many years ago, and it's not an easy task. People are at maximum tension! Best advice is to make lists of required shots. Don't want to miss any of those. Then take tons of "other" photos that just happen to pop up. Almost "point-and-shoot" style. If this was a paying event, you would be amazed at how many of those throw-away photos are "just wonderful, and captures the moment" (per the mothers-in-law).
I never took flash photo during the ceremony. Remember, this is a sacred event and you are just wallpaper. But, do have your ducks in a row for the photos right after the ceremony. They have other things to do and want to get going.
I wouldn't overly worry about the technical aspects of the photo event. You'll get good pictures and the people that look at your photos NEVER look at the photo, they only see the people in the photo. I had an outdoor wedding in August, in full sun (film days) and the film got so hot that it shifted color, became overly warm, almost reddish. I was devastated! I just knew this was a disaster! The bride's mother (my client) absolutely loved the pictures and never ever noticed the color shift!
Have fun and relax!