Plain ol' grass would also work, as it recovers quickly and you would avoid reseeding. Or any mixture of greens (lettuce, kale, collards, even dandelion which they really like) You may also want to plant some things outside your pen that the chickens can reach through to get at - comfrey is pretty tough and the chickens like it - when it flops you can cut it back to 3" or so and toss the spent leaves to the hens. If you have any nettles (standard field weed for me), they are very nutritious but the birds won't touch them unless you cut them (they lose their sting once the drying process begins). Sounds like a good plan, let us know how it works out.
