Obviously Snowpark has the best park hands down, but if you want a slope with bc and normal runs etc with a good park, either the Remarkables in Queenstown, or Cardrona in Wanaka depending on where you're planning on going.
You could probably get away with buying a Youth pass if you're buying day passes, but if you're trying to buy a season pass you would need ID.
hope this helps, have fun over here