Life In 19x19

I bought my kids some kindle fires and am interested in finding them some Go apps that would be good for kids or beginners. They have shown interest in Go but it is hard for me to find the time to teach the three of them at the different levels they are at (twin boys age 5 and girl age 3). I read hoping the might be some good apps they can use to learn and play. They all get the concept of Atari. Two of them get generic fighting and board placement. One actually can play through a 19x19 4-4 opening sequence.

Any suggestions would be greatly appreciated.

Thanks.