Sorry for the delay in responding - pesky work got in the way.
It was 246 points for the week including NYE. The "premium" is on the same slope as the gondola, so you ski right in/out. Children's ski school is at the bottom of the gondola, so it couldn't be easier. I think its a good value, given what they get for rental on those units.
Tbickford, you'll be there when we are! there are tons of special activities for NYE at the skating pond near the lodge. You can call keystone directly and ask, or check out the website. Also, there is a daily newspaper of activities that you'll get once your there that will help. Every night, there is a family event (one year we looked at the stars with telescopes, had a story hour, etc.)
Ski school - your twins are perfect to start (mine started at 3). Your are in River Run, right near the base of the Gondola. There are two ski schools - one is a half day snow play with a half day ski, and one is all day skiing. You might think about doing a few days of each, which is how we started our kids. That lets them ease into it. Unfortuantely, the program of ski/ply is at Mountain House, which is a bus ride from where you are, which can be a pain with two kids and everybody's stuff. The all day ski program is either at the River Run ski area (right next to the Gondola) or at Mountain House; the River Run area is very easy from where you are. Mine did all day ski at 4 - although they would occasionally stay behind with the instructor for a nap and miss the afternoon - but they had done half day 3 first.
Registering the kids is a bit of a nightmare; lots of paperwork and fitting of skis. We have learned to do it the day we get there, after unpacking and before dinner. waitiing to do it on the morning of the first ski lesson is a sure recipe for tears and frustration (not to mention what the kids feel like

). There are a number of packages available; we find the most efficient is to buy ski school lessons for the week; you get the kids' skis and ski passes with that.
Last bit of advice: there is a program where the kids stay at Mountain House one night at week (pizza, movies, arts and crafts) for free while Mom/Dad get to have dinner out. When you get there, call the activity line and they'll help you with reservations for both. It is always a highlight of our trip!
Now, for all this advice, you need to make me a promise: MAKE YOUR CHILDREN WEAR SKI HELMETS. They are available for rental, or you can buy them (we bought, the kids like to put stickers on them). You will also use them when you take the kids tubing on top of the mountain, which is way too much fun. I have seen too many kids hurt without helmets.