The units are brand new. Don't call ahead, most store reps will be unaware of clearance price drops this sharp and will make-up BS explanations like they were returns, damaged, etc. to block the deal to get it for themselves.
When you go to get the price adjustment, don't provide more information than you need to like where you heard about the deal or that you bought it online to re-purchase in-store, etc. Just ask for the price adjustment. If you're within seven days, you should be able to do it. If they say they can't because it's an online order, tell them you want to return and re-buy it. If they refuse, ask to speak to the manager and explain that you simply bought the item a few days ago and then later noticed that it's now on sale. Don't get into specifics of how the price is different online, and definitely do not mention that it's a clearance price. Just stay cool, and I'm sure it should go through. At worse, just return it. It's worth it, to get a brand new Wii U for 62.71.