PREPARE cake batter and bake in 2 (9-inch) round pans as directed on package. Cool in pans 15 min. (Do not remove cakes from pans.)
ADD boiling water to jelly powders; stir 2 min. until completely dissolved. Pierce cakes with large fork or skewer at 1/2-inch intervals. Pour jelly over cakes. Refrigerate 4 hours.
UNMOULD 1 cake layer onto plate; spread with 1/2 cup Cool Whip. Unmould second cake layer; carefully place on top of first layer. Frost top and side of cake with 2 cups of the remaining Cool Whip. Tint remaining Cool Whip with food colouring; spread on top of cake to resemble ice rink. Outline outside edge of rink with blue decorating gel. Refrigerate 1 hour.
DECORATE top of cake with candies. Add Teddy Grahams for the ice skaters. Decorate ice cream cones with green decorating icing; place around ice rink. Sprinkle cake with coconut and icing sugar. Serve immediately or refrigerate up to 2 hours before serving.