Make two small slits in the ping pong balls on each side
Push a straightened paper clip through the slits of the ping pong ball for an axle and add glue if necessary
Cut and glue the cardboard to make 1/2 of a box. Cut a window in the box. Use the corrugated fluting of cardboard to hold the axle of the ping pong ball. Because the flutes of the corrugation are parallel, it holds the balls parallel quickly and easily. Leave a good length of paper clip sticking out of the top of the box.
Bend the paper clip's extra length down 90 degrees, so they can be used as a lever to move the balls.
Use extra wire to hold the servo to the side of the box
Use more wire to attach the ends of the bent paper clips to each other (make sure the bend ends are parallel) and then again to the servo motor. Test the motion to make sure the eyes swing right to left without resistance.
Make a tongue shape out of two pieces of foam and glue just 2 of the edges so you form a pocket
Tape the buzzer to the bottom of the pressure sensor and put them in the pocket of the tongue.
Connect the power bit to servo bit, then use a wire bit to extend to the pressure sensor bit to the buzzer motor bit.
Put everything inside. I used pins to hold the eyes to the inside flesh of the pumpkin.
Sit back and giggle.