You don't want your drakes living with your chickens. Drakes have a penis unlike chickens. They can mate the chickens and kill them. If you had a lot of females, and the ducks don't share a coop with the chickens, they would likely be fine free ranging together. The minimum ratio of drakes to females is 1:4, but more is always better. You will likely have over mating issues with only two females. I have one drake and 13 females, and some of them were ove mated. In rare instances, 1:1 can work, but not advised. If you plan on giving the drakes and females separate areas, it can work where they are integrated only some of the time, like the winter when their mating drive is lower.
When you do introduce new ducks it takes a long time. You start out with the ducks in separate areas where they can see each other, but not interact. You want to atleast do that for a week or more. You will start to see them laying next to the border. Then you can introduce them in the same area, but now they can share the coop with a barrier between them. Again do this for another week or more. Lastly they can share the coop together with no barriers. You will need to see how they respond to decide if they need longer at any stage. Either way their will be some chasing likely. It can take a while before the ducks will accept each other, and other times it goes super smooth and they bond quickly.