Keara, do you have a rooster looking out for your flock? Just curious.
To the OP, I agree with your desire to feed less grain-based feed and more natural stuff, but I think they should be able to free-range to help them find a balanced diet. Great that you are planning a chicken tractor!
We free range and they eat a lot less packaged feed when they are able to be out and about, esp this time of year. We had a rooster for awhile and I felt that the flock learned a lot about looking for food and being safe with him around. We have hawks in our area- but the chickens just seem to know when to run and hide. I've watched them and they rarely stay our in the middle of an open area for long. There is nothing more relaxing than watching them scratch and hunt and peck.
I know that some just can't free range due to predators, and I am sorry for that- I think that is where a chicken tractor makes a great option!