I used a combination of my own narration, and some excerpts in verse from The Light of Asia
Siddhartha nearly died, but a girl passing by offered him some food, which made the monk realize his old life of riches didn't give him what he needed, but neither did this life of deprivation. It is compared to a musical instrument, the lyre, this middle way that he found. The key is not to make the strings too tight, or too loose.
I asked the kids if they had examples of "too much" or "too little" like this. Not really, so I discussed the Buddha's two extremes some more.
For our activity, I created a coloring page using imagery from the coloring book, and an image of a lyre. In the instrument, I punched holes so the girls could insert some glittery string, taping it on the back. Here is the Middle Way coloring page.