My yard is already full of duck and chicken poo, so I hear you! (small yard)
My duck pen is covered, so no worries about arial attacks by predetor birds. I want a few for the freezer and possibly a few more for eggs (people love duck eggs) but I doubt I need around 40+ ducklings. (nearest count...
I have 3 ducks on nests and they and my 2 drakes and a fourth duck who is not setting are very aggressive toward my 4 chicken raised ducklings. They chase and attack the Chucklings at every chance, tearing skin and ripping feathers. So the Chucklings run with the hens during the day and sleep in...