Yes, put the pump near to an edge so you can get to it easily, as well. You don't want to have to go wading around in there.
That clay in the little swimming pool will be plenty of soil for the water lilies. Have you planted them yet? If you get just one medium sized water lily, you will have plenty of coverage for your water in the summer to prevent algae from getting out of hand. You do want some algae to grow because the fish will eat it, and it also helps clean the fish poop out of the water - free fertilizer!
Plus a lotus plant in the other end, maybe? The lotus do get quite big if they're happy, unless you buy a dwarf one like mine. It's still 3ft across and has leaves about a foot wide. You can limit its size by the size of pot you keep it in, somewhat.
