I have seen posts like this before- always be better dressed than the guests. To a degree you are there to look like the hired help, not uncle bob's poorly mannered nephew...
As a general rule of thumb, I dress similarly to the bridal party. If they are in tuxes, so am I, light colored suit on the beach- well, I better get out my light colored suit, too.
Also ask the bride and groom during the consult or any subsequent meetings if they prefer you to wear something special. Its a service industry- you are there to serve the bride and groom, not your self. Not sure how I would feel about my photographer showing up in a t-shirt or even a polo with his company name. Feels a little too informal and on the verge of disrespecting your clients to me.
Giving out a business cards when you get the chance is one thing, wearing a billboard is another. :-p
All the best.
M. David Farrell, Jr.
~Buying a Nikon doesn not make you a photographer. It makes you a Nikon owner!
~Everybody has a photographic memory, but not everybody has film!
North America just north of that sharp right turn North America makes on the Atlantic coast.
You can never go wrong by asking the person that is writing the check what you should be wearing when you show up. In the end you are a hired professional and if you look around at weddings you will note that the wait staff are normally in some sort of pseudo tuxedo (white shirt and black pants). You don't want to be mistaken for a waiter, but you would like to be able to blend into the woodwork when you aren't taking photos.
I would recommend that if you are going to have to wear a jacket it will be worth your wile to get a jacket that is a little big and have it tailored to your needs. Explain to the tailor what you will be using the suit for and explain that you want it to look good, fit well, and have the ability to move with you. You will need the armpits lowered, and an expansion joint in the back, and if it has shoulder pads have them removed. Also have the pockets expanded to hold more film, and replace the pocket liners with heavier cloth, a good tailor may tell you that you shouldn't put things in your pockets, let them know you don't really have a choice, this is a work tool, not a true dress suit.
"Would you like it if someone that painted in oils told you that you were not making portraits because you were using a camera?"
"Shouldn't it be more about the joy of producing and viewing the photo than what you paid for the camera?"