It is often suggested that the kits can eat what mom has been eating, because she will be passing along the correct digestive bacteria that break down that kind of food. Under this theory, you would want to get mom used to the tractor and the wild foods before kindling. Start by feeding a few leaves of dandelion/violet each day along with the normal food, then up the amount a little at a time until she is eating whole handfuls of greens each day, along with her normal food. At that point I put them in the tractor, and only move it a little each day so they don't get too much greens at once. After a few days I just move the tractor normally.
Another option is to put a piece of plywood down, and the tractor on top of that. Each day, just move the tractor a tiny bit to expose just a little of the fresh greens. You can move it a little more each day, by the time it is off the plywood you probably won't need it anymore, just move the pen each day normally.