Unless the almost free condo at WP is also walking distance to the lifts, I'd suggest Copper. I think walking to the lift vs. packing everyone in the car or catching a shuttle will make the whole trip much more enjoyable for your wife. A slope side condo is also really nice for part of the crew to quit earlier or take a long lunch and relax. It's just a much better experience all-around.... what you want so your wife will want to come back!
Congrats on the strong negotiation. You will have a blast. Of course, I would ski Thursday as well if you are staying down in Denver that night. You get one more day on the slopes and you can still have dinner with your friends. I'd also probably wake everyone up early on Sunday and ski Sunday as well, but I am a nut that way and my kids are pretty hard core also. But I am willing to bet that your kids will appreciate at least one additional day - ski 4 if possible, no day off needed for you and the kids. You can go tubing at night, apres, or in MN. Don't waste your precious time at a real mountain with stuff like that. It sounds like you already know this, but it is really hard for people who haven't done it to understand how vastly different skiing big western mountains is from your home hill in the Midwest. The whole family will be blown away - and 3 days barely scratches the surface of what is possible at a single resort when you are talking real mountains.
tball offers up the best advice on this thread for making the trip fun for all - and a VACATION for your wife. You want to be as close to slope side as you can afford. Being able to slide in and out of the condo, rather than taking shuttles or ferrying around a rental car totally changes the dynamic. Proximity to the ski school meeting point is key as well (assuming some portion of the family is taking lessons). If you are slope side, your wife can peel off for the afternoon or start late if she wishes, and neither of you has to work too hard "project managing" the morning (i.e., getting everyone up, fed, dressed and hauling gear to a bus or packing everyone into a car that has to be parked in a lot further from the base than where you would typically park for a Vikings game). Trust us on this one. Proximity is where the paying a premium is worth it. My wife is a solid blue, resort-style skier, but she loves the mountain environment and ski in/ski out was the clincher that moved my wife into the "love" the ski vacation camp. Shuttles and cars make her feel hostage to the family logistical nonsense - it totally ruins it for her.
Copper is a great mountain. My favorite natural layout of the Summit County options. Just be careful on the altitude issues. It is real in CO and it could sour your wife on the whole thing. Lots of water, easy on the booze.
One other "pro tip" - find the spa nearest your condo, call ahead and hand your wife a certificate (including tip pre-paid) for a 90 minute massage. Consider it a down payment on next year's trip.