The recommended minimum for a run is 10 square feet per chicken. For a coop, it's 4 square feet per chicken. For chickens in confinement, where they never get outside, it's 10 square feet per chicken. These are not the amounts of space chickens do the best in, they are the minimums. They work for most flocks, most of the time. Some flocks with a mix of breeds or more aggressive breeds need more space.
I usually go 5 for the coop and more than 10 for the run. If you won't be using it as much, 10 would probably be fine.
I always recommend a run, even if you don't think you'll need one. It's often hard to say what daytime predator problems you're going to have, until you have your chickens. When there's not much of interest in your yard, they don't bother to stop by. After you have chickens, though, you can suddenly start having visits from hawks, coyotes, dogs, etc.
Runs are also great if you ever have anyone visiting with a dog or small children, have people over for a party where you grill out or ever have work done in your yard that will require a gate being used or left open. They also work great if you ever plan on taking a vacation and can't get a pet sitter to come twice a day at the correct times to let your chickens out and lock them up, if you make the run preditor proof.
Runs are also an excellent idea if you have a dog, as adding chickens to the family doesn't always go as well as you think it will. Once in awhile you get a chicken that likes to go over fences or other people's dogs run, jump or dig their way into your yard. It's not that that all of these things happen to everyone, but if they do, it's really tough to fix it in a hurry.
