I think you'll be fine as long as there's no delays. They should give you a tracking number to keep track of them. I would suggest calling your closest postal distribution hub to see if you can get notified when they come in and pick them up there. It might be a longer drive, but it would be worth it. Some people give their ducklings water or a small amount of food when they pick them up.
What kind did you get?
Also, Metzers has a live hatching cam on Fridays through Sunday. There's a different breed every week. I think this Friday's is the last one for the season. Who knows, you may get to see your duckling actually hatch live on camera.
Wouldn't that be amazing to see your ducks hatch (i've never used an incubator). I ordered two blue swedish, two buffs, two fawn and white runners, one blue runner, and two cayugas
I live out in the country (way out) so the pick may not be ideal, but i'll have to check for the nearest one.