Sunflower seeds have a natural herbicide in them, so be careful where you plant them. The oil is a preemergent and will stop most anything from growing in that same spot. This is why it is typically bare under a bird feeder. I think a couple of rows wouldn't hurt anything but the deer will eat them before they get to the point where they are producing seeds.
You can spray the young plants with this stuff:
http://www.gardensalive.com/product.asp?pn=2618 and it will keep them from eating the seedlings, or anything else for that matter. I have been using it for about ten years now and it is the most effective repellent I have ever used.