My ducks and chickens get along very well. Adult ducks can eat chicken food. Female ducks can be fantastic layers, my buff girl outlaid some of the hens last year. So the extra calcium in chicken layer feed is great for them.
I've heard conflicting things about medicated chick feed being dangerous, probably depends on what med is used. Anyway you should have unmedicated chick feed or duckling feed to start out with. Ducklings and chicks can't be raised together anyway, ducklings are way too messy and they get big super fast.
Ducks are unbelievably messy with their water, you can forget about having waterers in the coop. Which for me meant building a secure outdoor space for them attached to the coop, otherwise they'd be without water until I get up to let them out.
Another thing to keep in mind, drakes can be very aggressive with hens, to the point of killing them. So it's a really good idea to have a backup plan and a seperate place to put them if they don't get along.