Great Job! What a good idea to put it right off the deck so your youngster can help out. And I like the idea of using the under-deck space as a run, too. At our house, that space is usually reserved for hiding "junk" - like the lawnmower no one ever wants to put away properly!
I like how you attached it to the side of the patio deck. This allows for easy access to the eggs on the upper deck while allowing for the chickens to utilize the extra space under the deck for a chicken run. Great job.