If you are trying to keep some nice grass, I would sacrifice an area to keep the ducks. They will dig holes in the yard, eating worms and grubs. The noise might be a bigger issue, than smell, some ducks are more talkative than others though.Is it possible to "tractor" ducks with the chickens or does it get too hard when keeping a container of water for them to play in inside the tractor run? Am I being clear as mud?
So far we tractor around our 6 chickens in the front yard, small though. No way we could fit ducks in there so we are thinking of making a larger tractor coop/run with big wheels to deal with the swampy GA lawn issue. But will keeping a kiddy pool or what not for the ducks in such a thing I think it might be hard to get in there and dump the pool every night and refill where ever we move it the next morning and so on, not to mention add to the swamp (sinking in it when you walk) issues. We are trying to keep the grass nice!
The other option is to clear some land, not a lot of room there, on the side of the house and make a permanent coop/pen. It is closer to the property line though and might it get smelly?
(4 ducks and 4 bantams would be in it)