Yeah, theyre great pets. A kiddy pool is great (but you must clean it out every/every other day. They make really friendly pets and are really social. Mallards in the wild can't become tame, but if you hatch them as babies they are. The biggest problem with ducks is that they physically can't be potty trained. its no big deal though. Here are some hatcherys i recomend.
http://www.mcmurrayhatchery.com/category/duck_eggs.html
http://www.metzerfarms.com/
Most hatcherys dont sell 3 or 4 ducks (when shipped, they get too cold and can die.), so make a deal with your local feed store, and im sure they will take or buy the extra ducklings. Or you can find someone else looking into ducks or a current duck owner, and im sure you can sell the ducks to them. Don't buy the ducks before you have plans for all of the ducks, because if you want a duck you want to be well educated. I recomend this book for first time duck owners.
-Storey's guide for raising ducks
Also This site will give you lots of information on raising ducks, owners storys, everything. I totally recomend this...
http://www.liveducks.com/
They are great pets, but like i said, knoledge yourself before you get ducks. It will make the expirience much more easy and enjoyable. i hope i helped. =).
P.S. it is NOT inhumane to keep 3 or 4 ducklings in a kiddy pool. They just need acess to clean water everyday. You will need shelter for them too, (a coop, shed, hut... check out the books+websites they have LOTS of info.)
P.P.S. Peking ducks are domestic ducks but theyre feathers are more likley to get mites (still an unllikley chance if they have clean water.) Yet the peking duck is more tolerent to temperatures than the mallard. They are sometimes considered a better family duck than the mallard, but its not a fact. Mallards actually do happen to be domesticated ducks if you know where to get one. check out my websites, they have domestic mallards available.