Welcome to BYC!
I house both just fine. As little ones I did separate the ducks when they got too messy for the chicks, but at about 5 weeks they were all ready for the coop so out they went. I have 13 chickens and a pair of ducks that free range all day together and are housed together at night. Just make sure to have a nice covered area for the ducks since they'll be on the floor. Once in a while my ducks will "move" a chicken out of the way of a tasty snack, but for the majority of the time they get along good.
I had started with two roosters (on accident) and one was a menace to the ducks. He would really bother my female and eventually bothered the male so he went to camp freezer. The rooster I have now never bothers my ducks, and my drake never bothers my hens (mounting wise)
As stated you want to make sure you have lots of water. ...no really...a lot haha For winter I have one heated chicken waterer and three heated bowls. For summer I keep two chicken waterer (3 gallons) and one bowl (1gallon) for cleaning their nose. These get filled every day because my ducks like to play in them. We put a pond in for them and they hate it haha. Also, I keep all water dishes in my run to prevent wet bedding.