Hi flyingdragon!
I'm in Charlotte, so we're not too far apart. Some other breeds you might consider for meat & eggs are magpies & anconas. Unfortunately, I don't know anyone around here who has those breeds (well, I have some magpies, but they're not mature, so I won't have any for sale until next spring).
With about 15 acres, you're not going to have a poop problem unless you get a whole heck of a lot of ducks. I have one acre, and the ducks roam the neighborhood, but even with 30-some ducks, I don't have a significant poop problem (there's poop back there, but it's not egregious).
As for free-ranging, mine do during the day. But they are locked tight in Fort Ducks at night. Otherwise--the predators get them. I have learned this from cold, hard experience. And the nighttime pens have to be VERY secure.
I'd be glad to have you come look at my set-up some day if you are ever down this way and want to see one way of doing it. I also would be glad to sell you some Indian Runner ducks, but if you want meat birds Runners are not your best bet--they're very skinny.
Oh--as for the veggie garden--they will eat your young plants. I would fence it off somehow--the fencing does not have to be tough to keep ducks out--they don't like to challenge barriers. A mature garden is pretty safe, although they'll eat any low-hanging fruit. They'll also eat the weeds and pesky bugs, so they can be beneficial in a mature or fallow garden. Mine completely eliminated a severe Japanese Beetle problem within a year (and that was just six ducks on an acre).
Good luck, and let me know if I can help somehow.