Hi, there, I'll try to answer some of your questions. Welcome!
At this point, I think your ducks will either be quacking loudly, or mumbling. The loud quackers are females. Mumblers are males. That will happen even before a drake feather shows up.
Great that you have a kiddie pool for them!
(A little note - this is pretty much a G-rated site, you might want to review your comments there. There is an edit button.)
I feed my flock poultry layer feed, they do quite well on it. I also have Mazuri breeder as an addition to their basic feed. And I give them some treats, and greens, the occasional meal worms, they forage for worms and grubs, and like squash beetles.
How do you and the goose get along? Is the goose used to ducks? @Miss Lydia may be able to advise you better - she has chickens, ducks and geese.
I'll look at the photo more closely and see what I can see.
Looks like you have two Pekins and a Swedish Pekin mix. Lovely, lovely, lovely. Those breeds don't really fly. And if they're in a secure coop at night, that's pretty good. My Runners are much smaller, so I have them in a pen that's fenced across the top, due to hawks - even foxes around here will hop over a fence like mine (a meter high). I have another penned area with a net over the top - they go in there when I am out in the yard.
There are a couple of books I like - Storey's Guide to Raising Ducks, and The Ultimate Pet Duck Guidebook. But BYC is also a terrific resource, and it's interactive!
Edited by Amiga - 9/29/15 at 6:26pm