Don't let this game into your home if you can possibly avoid it. It is horribly addictive, and the words, "it's time to turn it off now" are always followed by, "no, no, please mummy I need to save the game, I just have to finish this, I need to save it" - this takes about ten minutes, if ds is not closely supervised.
Also, some of the games within it are a bit suspect. Ds mostly only plays pokemon, but there was one involving sheriffs and murderers that I wasn't very keen on.
I saw another child get into some inappropriate chatting, even with the friends function turned off. Ds knows not to do this, but I still worry that he'll see something dodgy. There's general chitchat just popping up in the corner of the screen ask the time, I don't think you can disable it.
In short, put this one off as long as you can. I do let ds play it, but honestly wish he had never heard of it.