So has anyone actually done a wedding and showed up in jeans and t-shirt or casual wear? Even if I was to change my mind and say yes I'm not a dressy up kind of person so wouldn't feel comfortable doing it...
Hmm...you do have to play the part, even if it goes against the grain. The guests will be a lot more cooperative if you look the part. It may be that only you, your pal and her Mum know that this is a "freebie" arrangement, and the last thing you need is the stress of guests expressing begrudged cooperation for the group shots, because "he's not a very professional photographer, is he?"
Wear a suit, have an assistant to round people up for the group shots, get a list (in advance) of all the happy couple and group shots the Bride and Groom want, and if nothing else, get those nailed. Do ask the couple to go through that list again thoroughly in advance to make sure auntie Elsie or cousin Bob haven't been missed out, and any informal shots you take thereafter are a bonus.
Also, don't take more than 45 mins to 1 hour doing the close family group shots immediately after the service...the crowd at the reception will get too drunk, too hungry, and narky when you reappear! The only thing thereafter is cutting the cake, which they may or may not want you to shoot.
And finally, you'll be jostling for position with dozens of guests with their own cameras for the couple's attention and best shooting angle for most of the day. Don't be scared to ask the entire crowd to hold back temporarily until you have got your shots, then let the rest get stuck in!
Best of luck with it, and enjoy the learning experience!
Cheers
George