I agree, I wouldn't be concerned that they are not ranging far at this age. As they get older they will start to venture father from the coop. Staying close to the coop till they begin to lay is not a bad thing. One of the challenges free rangers have is training hens to lay in nest boxes. If they stray from the coop for long periods of time too early you may find that they start laying where ever they find suitable.
In re: to feeding, at this age they need access to all the high protein feed they can get so I wouldn't ration their food. You can consider a wet mash which will help minimize waste and it is my understanding contributes to better absorption rates and hydration. I personally use fermented feed. I don't know anyone that has successfully raised chickens free range without some supplemental feed. It may not be realistic to think they will totally fend for themselves.
Make sure they have access to water in places other than the coop. I keep a couple watering founts in a shaded area at the edge if the woods. I've noticed that on hot days mine won't go to far away from water. When I keep water in the tree line my flock usually stays in the woods most of the day.
Good luck and have fun. Nothing better than watching a flock of free range chickens doing what comes natural.
