Yeah, I've flown with and used both QSteaming and Virgin's WiFi entertainment system. I've loved it every time. If you are taking your own device (iPad, Galaxy Tab, whatever) just remember to have it charged fully before the flight!
Remember they also have main screen movies in conjunction with QStreaming.
I don't think they have it installed on international 767's but I might be wrong.
Now for the techno geek side of me:
The Nexus 7 or iPad Mini both make excellent tablets for younger children. They both have parental controls too, so you can decide what media and we pages they can browse.
Just remember that, although more expensive the iPad has a much larger selection of both apps and TV
Enjoy the holiday!
Durban. Melbourne. Denver. Hong Kong.