I think there are lots of unformal grooms on bdw!! I think, however, that he should be wearing a contrasting color to your dress, maybe white, or one of your wedding colors? As far as the father, if the groom is going unformal, so should he! I think it may look off if he's wearing a suit, and the groom isn't, but then again, it's whatever everyone feels most comfortable in! Also, khaki goes great against the color of sand versus something too dark!