Preheat oven at 350 degrees F.
Prepare a 9 x 13 x 2" pan with cooking spray and flour.
To prepare crust, combine 2 cups cookie crumbs, 1/4 cup sugar and butter in a small mixing bowl. Press firmly into prepared pan. Bake for 10 minutes and then chill.
To prepare filling, combine cream cheese and 1/2 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 1/2 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 1/4 cup 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.