Combine graham cracker crumbs, 1/4c. sugar, and butter together and press firmly into the bottom of a 13x9-inch pan. Freeze for about 15 min. Meanwhile, mix the cream cheese, 1/2c. sugar, and 2T. milk together. Fold in 1&1/2c. cool whip. Spread this mixture over the graham cracker crust. In another bowl, prepare the instant chocolate pudding as directed on the package except use 3&1/2c. cold milk. Pour pudding over the cream cheese layer. Chill for several hours or overnight. Spread the extra cool whip on top (the rest of the cool whip container). Keep chilled.