Ancona are a pretty desirable duck these days. You may have luck finding someone else in your area who would be willing to take them. I would personally keep my ducks a little overcrowded temporarily to prevent them from going somewhere I didn't agree with. You can always just float the idea on...
I don't deal with them where I live, but I have read enough horror stories about snapping turtles too. Land predators are not the only thing to worry about. And yours can't fly away, which is the main way wild ducks escape predators.
Those ducks are going to need a minimum of 16sq ft. They...