Thanks so much for all of the nice comments! I'm not sure which came first, nice people, or their chickens.
Yes, it is a self-latching door, and yes, I made my husband drill a hole for a string to put through so we don't trap our children, or ourselves, in with the chickens!
I don't mind at all if people copy our idea. We can provide more details, dimensions, pictures, etc. if people are interested. My husband designed it as he went, so his measurements are on a lot of different sheets of paper, but we could cobble something together. I got so much out of this forum and used many of your ideas while I was planning, so I am happy to share as many of my ideas as I can.
Oh - and this playhouse you might know, is normally around $300, so plan for that in your budget if you want to try to make this coop. We were certainly lucky when we got that price.