I highly recommend Star Walk 2. Just recently, I visited my cousin and showed the app to my nephew, by mirroring my phone screen on their 75-inch TV (BTW, they bought this TV with BTC... Soon to be the most expensive 75-inch TV in the world!). Anyway, my nephew was TRULY AWED by the graphics and the ability to go forward/backward in time and watch the celestial bodies' trajectories as they move in the sky. Also, the ability to zoom in and discover faint, distant objects that don't even show up in the standard zoom, which are also clickable, with descriptions and info. It also uses the phone's gyroscope/compass, together with GPS, to show you the exact part of the sky the phone is oriented to, in your location, and the viewpoint moves in real-time as you move the phone. Just awesome.

It may not be scientific-grade s/w, but it's 100% worth buying by anyone even remotely interested in astronomy, and certainly those who have kids in the family.