That's cool.
I started one once. It went wacko when I started cutting the door.  I never finished it. I'm a quitter......
Didn't really want to do it in the first place.  It was old and in bad shape to start with.
Screwing the staves would have helped a lot.  Your son was smarter than me.

It looks good. More important though is spending the time with your son. 

Figuring out how to do something you have never done is what makes a good challenge.