Most of the time my Muscovy girls will stay on the nest 2-3 days after first ones hatch. Hopefully your Muscovy will stay until all have hatched. If you put food and water close by they will be fine.
What a serious look lol I always keep mama and ducklings with everyone but safe behind lattice that I have stapled fencing to so the ducklings can't get through and out with the adults. You just never know how one might react and I would rather be safe than sorry.