Whew! Jack was such a good sport and wore it ALL DAY at the convention with no problems. I'm glad that I decided on flannel because it wasn't too hot like fleece would have been but it wasn't too thin and flimsy like a cotton print might have been. I've already washed it three times and it's holding up great!
I will try to upload a pattern or basic sketch of how I made it in the future. Let me know if you want it!