Uh, you may want to reconsider getting ducks since you have many of your fishes in ponds. Ducks have a way of finding their way into ponds and eating/attempting to eat/mutilating the inhabitants of said ponds. And fences around the pond don't help unless there is a cover of some sort. Another thing to remember is that adult ducks tend to defecate a ton, and they seem to really enjoy doing so in the water thereby majorly increasing the bio-load of your pond(s).
Trust me on this one: we used to have some ducks and I lost a few small koi that after the dumb things ate their fins; they also made the pond pretty gross.
If you still want to get ducks, head out to your nearest Tractor Supply store (should be one relatively near you) and purchase all the essentials for raising them. These items include: heat lamp, heat lamp fixture, wood chips (bedding), watering container (don't just use a bowl, they may drown/swim in it when they are young), starter/grower feed (first food to feed them; foods need changed as they grow), and a feeding container (once again, don't use a bowl in order to help keep feces out of their food).
You'll also need a fairly large container to keep them in while they're growing out. You can make their permanent home while they're growing out; I'll get you the details on square footage and stuff after I look it up from my book on keeping ducks.
As for breeds, I would avoid the common mallard since they can fly which makes containing them a real pain since ducks love to explore. If you want tons of eggs, consider getting Khaki Campbells (tan-colored ducks) or Indian Runners (also known as penguin ducks because of their posture). If you want to eat them, then get Pekins (giant white ducks). If you want really big ducks that can fly and will roost in trees for sure, then go with Muscovies (big, warty-faced ducks; have pretty wicked claws). There are many other breeds, but the ones that I named are usually pretty easy to get.
One last thing that I have to say: get at least four ducklings (preferably six) so that they'll still have friends in case a few die when they're young (which sometimes happens; it's sometimes inevitable).