As some one who has worked with thew fish and game dept for years.you had better check with you local dept. as in most states it is illeagal to raise and release unless you are a licensed game farm. There are many carriered diseases form domestic to wild game . Even if your ducks appear healthy you don't know what they may carry . We just had a guy turn loose his deer and it cause a problem as they had a mouth disorder that cause the death of a small herd that as tax payer we had gotten started in a area again. all had to be KILLED.
It's a noble and nice idea to try to help nature regain balance but it has to be done in the proper way or it can be even more devastating to the wild population.