Every plot idea and plan, no matter how big or small, should be off limits to everyone except GMs, man. Any good GM would know that. Why wouldn't this not be apart of the plot? Do you wanna just start spurting to everyone that we are gonna do that? Come on. Just try not to do it in the future. Talking about future plans of the RP to others is what tainted the first War a bit.
The first one for sure. But you should also consider having neither of them in it. They already know it's the sequel. You can always just put War Between Pokemon & Humans: "blah blah blah". But if you decide not to, the first one looks best.