It is common for photographer to feel like a fish out of water with this kind of work. Even expected. Especially guys. Just like rendering Depth of Field and Motion are optical truths for cameras, our friends get married. Have babies, graduate, and stuff. I used to resist this but I have come to realize this is a gift you can give and it is part of life. This is a photographic rite of passage. Be the Shaman asked to do a healing. These photographs will become part of your and their history. Embrace it. Love it. Do not get caught up in the drama of the day. Use the energy of the day to enliven your spirit and not the drama of illusion. You are already good, go with it. The photographer gets to remain in flux. Make lists of stuff you want to do/shoot/light and be OK with departing from the list. Explore back button focus in servo, and practice it. Use a diffuser or a gary-fong (totally worth it) on your flash. ETTL, and drag the shutter if you are feeling up to it in dim/crap light so there is some background. Drink. Tell everyone what you are doing while you are doing it..."Relax I am going to take more than one photo!" etc. Do not be afraid to be in charge when shooting groups. Shoot groups in soft light with a tripod and expect to do head swaps. Tell them dirty jokes. No one will expect that and will remember you. After everyone is hammered switch from Raw to Jpg.
OK now where are those Damn LR3 presets I came here looking for...