The upper mountain never really gets busy. Lower mountain is full of families and kids. Lots of people talk negative about nakiska but it has all high speed lifts, good grooming, and lots of snowmaking (to make up for the lack of snowfall).
I can get more distance and vert/hour there than anywhere else.
There's also talk of another expansion, apparently opening up another few hundred acres or so of upper mountain terrain. IF that goes through it'll make it more enjoyable. Still won't have the snow of LL or Sunshine, but I've had some great powder days at Nakiska.
Very enlightening info, I wanted to try castle this year as well, ever make your way down there?