Kinderclavier^TM features a set of piano/keyboard learning books that enable learning from a very young age.  

Using colour-coded letter stickers to be pasted on pianos (easily removable subsequently too!), young children can play familiar songs as soon as they recognise the Alphabet!  Makes a great confidence-booster and paves the start for a music-learning journey in later years.

 

In book 7: Book 7 is recommended for ages 3 and up.  Its filled with familiar hymns for children to enable learner to play about 30 of them!