I see plenty of kids on Miiverse, so the notion that "kids don't play Nintendo games" is false. Also, a majority of people playing video games are teenagers and adults, and they're the main demographic of PlayStation, Xbox and Steam. Nintendo needs to reach out to everyone, not just kids OR adults.
Yeah, my daughter's 9 and her platform of choice is her 3DS. She has her own Iphone, she has her own Ipad, but her top choice tends to be the 3DS. Granted, she's my daughter, and when she walks into my office and sees my shelves and shelves of Nintendo games and systems, and when she sees my copy of Nintendo Force arrive in the mail every month, there's bound to be some artificial bias there.
But man, I checked her activity log the other day, and she's put 140 hours into Animal Crossing, 30 hours into Tomodachi Life, 10 hours into Disney's Magical World (not as big a hit), and 50 hours into Style Saavy. It's almost embarassing for me, because I originally bought Animal Crossing for myself, I'm the mayor of our freakin town, but she schools me on that game constantly. I've never even been to the island!