Why'd you want to play N64 with mouse and keyboard? I did it on the Mac/PC and it is awful, even the shooters like Golden Eye and South Park are not good to play with it.
When it comes to Wiimotes and sixasxis: you can use several Wiimotes at the same time and you should be able to use several six axis at the same time (I tested the first and I read here that you can use two sixasix, so this should work).