Is it not as hot as the hubs of Hades in southern CA in June? The jacket issue might just solve itself, if the ceremony is outside. If your groomsmen all wore white shirts with red ties and red hose, with whatever tartans their kilts are in, and you a white shirt with a black tie and black waistcoat, with black hose, and leave off the jackets altogether, I'm thinking it would make a fine presentation.