It's not as motion-controlled as the Wii, and as yet there's not really a 'Wii Sports' equivalent. Think the 3 year old would struggle. On the other hand MK8 Deluxe has settings that make it almost autopilot which is good for kids.
Humm good advise.
So there are no party games for it?
there's a few, snipperclips (new version incoming) is meant to be good. I've not looked much into it yet tbh.
nintendolife.com is pretty good as a resource for what is out there.