I will use two long balloons, attached to the front just behind the wheel and then attached to the axle on the back. In the front, i will take apart a clip and clip the two balloons in place.
That will ensure that the two balloons will stay. This balloon car will not need air. To power the car, you will need to wrap the balloons ends to the axle and roll the car backwards, as a result, the balloons will wrap around the axle stretching the elasticity. The greater the times the balloons are wrapped around the axle, the more rotations there will be in the wheels.
As for wheels, I will try to find a light sturdy material since the frame of the car will be processed stud wood, the type in your walls. I chose this type of wood because it is fairly light, but heavy enough to keep the car on ground
I hope my idea will work as planned