well now it will depend on where you are located. Ducks wear down so they don't need much except for protection from predators and extreme windy conditions. Fresh water is a must so if you live were it gets below freezing you may want to invest a heated dog bowls or buckets so they will have fresh water. Inside my duck house I have a thick layer of pine shaving about 10-12" more by end of winter, they snuggle down into that to sleep but most of the windows stay open all winter long bottoms closed tops open so they have good ventilation which is very important.
Of course you can keep them together as long as you don't leave food and water inside the coop and the only reason being the ducks will make a mess water will be all over the bedding and they will keep the feed messy too. As long as you realize when these chickens and ducks mature into adults if you have a drake among the ducks he will most likely try to mate with your hens which will be a death sentence for them. But if they are young you won't have to worry about that till next spring and devise a plan to separate them . But give them adequate shelter, protection from preds and fresh unfrozen water and they will be a happy bunch. Ducks have a wonderful way of keeping warm with their down under their feathers so even in Minn. they should be fine.
