The answer to your consideration is YES. You need some ducks.
They are messy but you will love them! They are a big pain with water, but they are so funny and cute that they make up for it. And we finally figured out a solution to the water mess (an enclosed "washroom" that has a tub in a wire-covered frame to catch splashes underneath their water bucket) and now our bedding is nice and dry. I can post some pictures if you'd like.
As to your other questions
Some people have put their ducks in with their chickens, but having kept both (not together) for a few years...I wouldn't necessarily advise it! Ducks WILL get the coop wet (unless you give them water only outdoors or figure out some sort of water-containing system), and chickens prefer being dry! As BarredBuff said, they are definitely messy little buggers, too! They WILL murk up any water they can reach, and will splash it as much as they can. Their droppings are also wetter and more abundant than chickens, due to all the water they drink (being
waterfowl after all
). It would probably be easier in the long-run to build separate housing if you can, but housing them together
can potentially be done.
I'm sure you can find some BYC'ers who have figured out a workable solution to keeping both together, so if you'd like to hunt around for threads, I bet you could find some. It just may take some work and planning (separate water stations, for instance). I've heard people suggesting putting a waterer up where the ducks can't reach for the chickens so it can stay clean (in addition to one for the ducks at a lower level). Most ducks can't fly or jump well, and chickens are expert hoppers. Also, I don't know if you use pelleted feed for your chickens, but as a tip, I've found that pellets work well for ducks (who can't scratch and peck up crumbs as well as chickens). I've used pellets with my adult ducks for a long time, and I don't think a whole lot gets wasted.
You don't need a male (drake) for the duck hens to lay eggs. In fact, if you keep ducks with the chickens, I've heard drakes can potentially actually seriously injure chicken hens if they try to "do the deed" with them.
Hope this helps! You should try ducks! They're fun!