If they were mine I'd just do lockdown a day early. Not going over 50% humidity at first, but just stop turning on day 24 to give them time to get into position to hatch.
It's unclear right now whether you will need to assist, it probably will hatch on it's own but maybe a day early.
That's a saddle air cell. Were they shipped?
They should still take 28 days if your temperatures are right in your incubator.
These are standard size magpie ducks and not call ducks right?