Well, this game is pretty bad. Terrible graphics, annoying voice acting (shut up, Dora!), and atrocious kinect 'sensing' - fairly certain you could stand there and move your arms once or twice to get three stars (the highest amount).
Seriously, my four-year-old daughter has failed to get anything less than three stars on any song, and she (for the most part) ignores the characters and dances her own dance...hell, even my two-year-old got 2.5 stars by being in range of the sensor and walking around!
On the plus side, I have to say they both love it, and the achievements are easy (if you want them) - I would say three hours max for the 1000g (no mind-numbing five hour grind in this one!)
So, if your kids love Dora, the Bubble Guppies or Team Umizoomi and you love achievements, then this is the game for you.
If you want an actual kids dancing game, then Just Dance Disney would be a better bet, although this is definitely aimed at much younger children.