Preheat oven to 350 degree F. For crust, in a medium bowl combine graham crackers, pecans, and 1/4 cup sugar. Stir in melted butter. Press crumb mixture onto the bottom of a 13x9x2-inch baking pan. Set aside.
For filling, in a large mixing bowl beat cream cheese, 3/4 cup sugar, and vanilla with an electric mixture until combined. Add eggs all at once, beating on low speed just until combined. Stir in mashed bananas. Pour filling into crust-lined pan. Bake for 30 minutes or until center is set.
Meanwhile, in a small bowl stir together the sour cream, creme de cacao, and rum. Spoon sour cream mixture over filling, spreading evenly; bake for 5 minutes more. (Sour cream layer may crack slightly). Cool in pan on a wire rack. Cover and chill for 4 to 24 hours. To serve, sprinkle with toasted coconut. Makes 20 servings.