As you may know Keystone is not known for tons of hairy expert terrain, but if the house is slopeside at Keystone it would be crazy not to spend at least a couple of your days there unless you are super hardcore. Perhaps early in the week when you are acclimatizing and late when you are tired. There are some bumps on Keystone's North Peak and pretty glades in the Outback for better skiers, and you can catch snowcat rides or hike to bowls above those two mtns that are fun, single black diamond in difficulty. And of course, tons of great intermediate cruisers.
Arapahoe Basin is about 3 or 4 miles away from Keystone and is a MUST for advanced skiers. Hopefully you will catch it with good snow. JimH is probably right about the Vail Resorts multiday pass, otherwise Copper and especially Loveland can be skied for less on a day-ticket basis. Check out www.liftopia.com for some ideas if you want to buy a-la-carte day tickets. Also, your NSP status is likely to get a decent discount at some places, for example Copper Mtn.
Welcome to epicski and congrats on your neat prize!