Place orange slices on foil-lined baking pan. Sprinkle with 2 tablespoons of the sugar. Broil 4 to 6 inches from heat for 10 to 12 minutes or until golden brown on each side. Set aside.
Place ground coffee in filter in brew basket of coffee maker. Add water to coffee maker; brew as directed. Cool coffee to room temperature.
Pour coffee into blender container. Add ice, rum, cream, 2 of the charred orange slices plus any juices from the pan, remaining 6 tablespoons sugar and allspice; cover. Blend on high speed until smooth. Pour into beverage glasses. Cut remaining 2 orange slices in half; skewer with party toothpick. Garnish beverages with whipped cream, a sprinkle of additional ground allspice and a skewered orange slice.