After making the helicopter, we were taught how to make a wind powered straw car. This was quite challenging, even for the adults. It is quite difficult to explain how to do this, so I will just post the photos.
Instructions on how to cut the straw
Inserting rubber bands through the white straw and attaching the ends of the rubber band to a propeller.
This young boy on the left could catch very fast and was demonstrating how to cut the straw car.