For Cake: Line half sheet pan with parchment paper. Attach half sheet pan extender.
Combine flour, baking soda, spices and salt in bowl; set aside. Beat sugar and eggs in bowl of mixer fitted with paddle attachment on medium speed until light yellow in color. Mix pumpkin, water, oil and vanilla in separate bowl. Add to sugar mixture; mix well. Add combined dry ingredients, mixing just until combined and scraping bowl as needed. Do not over mix. Fold in 10 oz. NILLA Wafers pieces. Spread batter into prepared pan. Top with remaining 2 oz. cookies.
Bake in 350°F standard oven 45 min. or until internal temperature reaches 195°F to 200°F and center of cake is firm to the touch. Cool completely in pan on wire rack. Cut cake 5 x 6 into 30 pieces.
For Tres Leches: Mix ingredients until blended. Refrigerate until ready to use.
For Whipped Cream: Whip cream and sugar to medium peaks. Refrigerate until ready to use.
For each serving: Place 1 cake square in shallow bowl. Top with 2 oz. Tres Leches and let stand 5 min. to absorb. Garnish with 1 oz. Whipped Cream, 1/2 oz. NILLA Wafer pieces and 1 tsp. pumpkin seeds.