This being my first 3DS game, I decided to play mostly in 3D with the control pad. I say mostly because there are some levels in which you must play with the accelerometer, so I temporarily switched to the default setting for those levels. I would recommend, as would Nintendo, to let children 6 and under play only on the accelerometer mode because it is in 2D. And frankly, I found that both control schemes have the same level of fun, just in different ways.
In terms of violence, there is no blood, and the characters simply shatter into cubes if they die. The only weapons in the game are shurikens that can only be used once, and to get them, you have to collect these scrolls throughout the game to get them. I never did use them because there really isn't anything you can use them on except the bosses, and even then, you still have to do specific non-fighting things to win. There is a setting in which you can create your own level and share it with friends, but it utilizes QR codes and not the Internet, making it very secure. Overall, it is a good puzzle game, and I would recommend it for long trips and such.