I dunno. My gut tells me that to reach that audience you have to find something new every time. The audience isn't into gaming normally, so to keep them interested you have to keep things fresh, instead of relying on a established franchises. I wouldn't be surprised if the software that is a hit in all demographics won't be Brain Age, but a completely new game that makes perfect use of the strengths of the 3DS*.
*Problem is that 3D doesn't really offer a lot of new ways to play unlike the touch screen did for the DS. But perhaps we'll get surprised. I liked that fake "zomg 3DS footage" video with the game that makes clever use of the camera of the DSi to create "3D". I would never have thought the camera could be used for such awesome things. Perhaps the 3DS will bring the same kind of creativity in software, and maybe the surprise software that expands the audience will come from that direction instead of Brain Age or Animal Crossing and the likes.