Muscovies are reported to be wonderful mothers. BUT, IMO, you're wasting good eggs by leaving eggs in the nest. They are at risk of being broken, and if so, eaten by the ducks. Are they being laid in a secure coop that is closed up at night? If not, the eggs may attract predators. Not to mention, leaving eggs around may result in stinky rotten, exploding eggs. If your ducks choose to go broody, you'll know it. You won't be able to get them off the nest if they are broody. That's the time to let them set on eggs, and not a minute before then. So, IMO, gather those eggs up, take them in the house, and if they pass the float test make a great omlet and do some baking. Hold back a dozen eggs, always rotating so you're saving the freshest ones. That way, when one of your little ducks goes broody, you have some fresh eggs to give her.