Yes, you do have ample enclosed space, imo!
My chickens are in a bit less than yours (4 birds). I have had them 2 years now. I started off planning on a free run of the garden, but I am afraid I love my garden too much. After the bad, bad girls did lots of bad things like eating all my pea seedlings they became run dwellers. They only get let out occasionally when I am around for strict supervision. They are absolutely fine, lay very well, and seem cheerful so far as you can tell with a chicken. If they are unhappy, eg food run out, they let me know by making an absolute racket, so I think they would be able to communicate (or get ill) if they weren't OK.
They have a deep layer of hemp bedding to scratch in, greens and corn as well as layers pellets every day, plus cabages etc (bolted ones excellent at this time of year!) hung from roof.