I came with an idea polystyrene balls which would float and fall in the air. First I made few sketches:
My idea was to demonstrate circulation of breathing, or to demonstrate a 'sigh' when the air stops to blow. Here you can see what happened:
In my second attempt I used the same ball but this time I attached them to each other and to the frame using fishing lane. Also I used more powerful ventilator:
The balls were moving the way I wanted, the only problem was that they did not move too much. I came with an idea to put light cellophane stripes between them to give the air more grip. Here is what happened: