I dont know if this is any help but have a look at the link below..as there is a link on it with pictures its a bit on the big side but should be easy to make smaller...MM.
That's the kind of thing. I'd probably go gor something slightly less feral though :-) My toddler has a cloth cubby house. I had a thought to take it's measurements and scale up.
Our neighbors had a custom canopy built in their back yard. I've been looking into doing something similar because some of my favorite plants are shade lovers. Unfortunately the 3 largest sides of our property are almost full sun. Have you looked into doing something like this?