I hear that sunpeaks is better than big white but i don't know from experience.
If i had that much time and flexiblity i would probably not get to planned out. I would just go with what the forcast is like. There is also White water in nelson bc that is supposed to be unreal. Red Mountain is fun but not very big so unless the snow is good (which it usually is from what i hear) then there isn't tons of stuff to ride.
Castle mountain is near Fernie and again i would just let snow dictate which one you go to.
Kicking horse has almost no beginner terrain, so you might want to consider what yours and your wifes skill level is. There are some mildish runs to get you off the top ridge but it is just a cat track so kinda boring to be lapping that all day.
My guess is that after a few months in BC you will be much better and both be able to ride a lot of terrain at any resort.