I am also getting married in south Maui in early Oct next year, and my WC thought that 4pm would be a good time to start, that way we can have time to do cake cutting/toasts, take photos, and then be ready for sunset photos at 6pm. Our dinner will start around 6:30, and then we'll carry on till 10pm when the restaurant closes. I think it will depend how quickly your ceremony will be, plus how many photo's you want with guests or your bridal party before the sun sets.