Heat oven to 350°F. Line 13x9-inch pan with foil so edges extend over 2 sides of pan. Cut cookie dough in half crosswise. Cut each section in half lengthwise. With floured fingers, press in bottom of pan. Bake 15 to 20 minutes or until edges are golden brown. Cool completely in pan, about 15 minutes.
Use foil to lift cookie layer from pan; remove foil from cookie. Place cookie on large serving tray or foil-covered 14x10-inch sheet of cardboard. With long side facing you, cut 3 1/2x3-inch rectangle from upper right corner of cookie. (See photo.) Cut rectangle in half lengthwise; reserve for bus door.
Reserve about 1/4 cup frosting. In small bowl, mix remaining frosting and food colors until well blended; spread frosting over cookie.
Place sandwich cookies on bottom for wheels; use some of reserved frosting to attach gummy rings for hub caps. Cut blue chewy fruit snack roll to fit, and place on cookie for passenger window, windows on door, and driver's window; cut red and place for stop sign. Attach wafer cookies for driver and students' faces. Use remaining ingredients to decorate as shown in photo. Color very small amounts of reserved frosting for smiles, eyes and hair as desired.