Preheat oven at 350. Prepare a 9 x 13 x 5 cm pan with cooking spray and flour. To prepare crust, combine 2 cups cookie crumbs, quarter cup sugar, and margarine in a small mixing bowl. Press firmly into prepared pan. Bake for 10 minutes and then chill. To prepare filling, combine cream cheese, remaining sugar, and half cup Cool Whip in a mixing bowl. In another mixing bowl, combine boiling water into gelatin until completely dissolved. Mix cold water and ice cubes together to make 1.5 cups. Stir ice water into gelatin until thickened. Remove any remaining ice cubes. Spoon gelatin over cream cheese layer. Refrigerate 3 hours or until firm. Spread remaining Cool Whip over gelatin layer. Sprinkle with remaining cookie crumbs. Decorate as a "grave yard" by poking sandwich cookies on end into dessert. Decorate the cookies as tombstones with the decorator icing. Scatter candy and pumpkins around the surface.