I decided on the large gray plastic storage bin as the duckling brooder. It allows them plenty of room to move around as they're growing (they grow very quickly), has high enough sides to prevent most of the water they'll fling around from going anywhere outside of the bin, and will also prevent these little cuties from escaping as well.
The gray bin had previously suffered some damage while being used as a chick brooder; the heat lamp had fallen, leaving a melted gaping round hole through the bottom of the bin at one end, so repairing this was the first step.
I took the bin to Andy for help in figuring out how to seal the hole, and after he asked some questions, he set about fixing the bin for me.
He cleaned up the hole by cutting off all the melted plastic, leaving clean smooth edges, and then he decided to use some waterproof caulk and a couple relatively thin pieces of wood, sandwiched on the outside and inside of the bin, and then screw those pieces together for a really secure fit.
After the caulk was done curing for 3 hours, I brought the bin back inside, put a layer of pine shaving bedding down, added a food dish with pellet crumble, and then started the last part of this special project: the duckling shower/tub.