Sunflowers why not save your back. Just put down a layer of cardboard or newspaper then spread your top soil over that. The cardboard will smother the weeds and eventually brake down. I would advise you cover the entire area with cardboard paths included.
This is a great opportunity to try lasagna gardening. On top of the cardboard layer grass clippings, leaves, household scraps (no meats or milk products) egg shells, coffee grounds, compost and your top soil. You'll never regret it. This link may help.
http://organicgardening.about.com/od/startinganorganicgarden/a/lasagnagarden.htm
I know that you can use newspapper for this too. Our local paper has a lot of color photos in it. Is it safe to use or not? And what is it about color inks that makes them so bad.
Thanks, Jack