You'll want at least two cards per camera, because when one is full you can switch and have a data tech dump the first.
And yeah, the reason everyone is asking "two cameras, are you sure?" is because most shoot with one camera at a time on a film set. Multi-cam is great when you can pull it off, but you need more crew, lights, setup time etc.
Not a huge fan of P2 cameras, but whenever you do multiple cameras on the same production it's ideal if they're all the same. I'd stick with two of a kind.