Take a moment to thank your parents and siblings and tell them you love them. This is a sweet but an emotional day for them!
GET MARRIED! Smile and enjoy the day that you have been planning for. Do not waste one minute worrying about your gown once the ceremony is over. No matter what you do, it will get dirty. Amazingly wedding gown cleaners/preservationists can work miracles later. Your gown will look good as new.
Enjoy your wonderful wedding day and cherish each and every moment!