Stir orange juice, pineapple juice, simple syrup, coconut-flavored rum, 151-proof rum, grenadine syrup, and fruit-flavored liqueur together in a 2-quart or larger pitcher. Refrigerate for at least 2 hours, or overnight.
Place 1 cup of crushed ice in each of eight 12-ounce glasses. Pour about 1 cup of rum mixture into each glass. Garnish each glass with a maraschino cherry and an orange slice.