i do have other ducks but not muscovies. and we dont really have predator problems eny more we took care of that.Do you have other ducks? Its always easier to adjust them to a new place if there are other ducks they can follow.
I would keep them cooped or penned for at least a few weeks. That will get them used to you and their new surroundings.
And maybe create some sort of schedule that they will look forward to. Like feeding them at night.
I feed mine first thing in the morning when they all get let out for the day and again at night. So come night time, they are all near the door to their coops waiting to be fed and put in for the night.
And muscovy ducks don't care too much for ponds. Mine seem to prefer a small tub or water or even puddles. I rarely see them swimming like the rest.