No, really, you shouldn't have done this.
Anyway, since people have asked, here's a step by step guide to turning off this unwelcome feature and keeping your household from turning into the mall scene from Minority Report.
1. Turn on your system (so far, so good!).
2. Tap the wrench (System Settings) in the Quick Start Menu.
You can also do this in the standard Wii menu if you'd prefer.
3. Tap the wrench and on/off button (Power Settings) at
the bottom of the System Settings menu.
4. Tap the large icon that appears in the center left
of the screen.
5. Tap the "Quick Start Menu" button in Power Settings.
6. Tap the "Wii U GamePad Alerts" button. (You can
also turn off the Quick Start Menu entirely if you
want quick access to your system's legacy Wii
7. Tap the "No" button. With reckless abandon.
8. Your Wii U is now free of intrusive, annoying
ads, the way nature intended!
9. Show Nintendo what you think of this new feature.
If this guide was useful, spread it around! I could always use the hits.