Yes, pre-formed plastic ponds are easy, but will cost you about C$200 or f you have some land, you can dig a hole and lay down a rubber pond liner. For a pond, you'll need filtration and like you said, predation from various mammals, birds and nosey humans. You can build a screen to put over the pond if the pond is not too big. If the pond is deeper, over 2 feet and has some hiding spots, the RES should be OK from most mammals. But I have heard about some crafty raccoons, but 2 feet generally is enough.
Depending where you are, temps should not be a problem for RES. But the Chinese softshell is a subtropical species and it may be too cold for it outside especially in many parts of Canada. I am in Ottawa, and my water outside in a pond is around 12C only.
Cheers,
JJ