I am in the same boat as you, as I'm also going to a summer wedding, except it's in New England. I think a white oxford will be a good go to, but maybe not with a three piece. I'm wearing it with white jeans and a navy jacket. Check the what are you wearing now for images.
I recently just picked up two ATM slub tees, one in white, one in black, to be worn in hotter summer weather. They are very, very light and airy. The material is so light that only gentle hand washing is recommended. Does anyone else here wear ATM tees? What are your thoughts?