I was someone who learnt to play the piano with Alfred's lesson books at a young age and when I started teaching, I used them for my piano students with great success. I know a lot of people have their own style of learning/teaching but for anyone with younger aged kids (5yrs - 10yrs) I highly recommend Alfred's Piano Lesson Books.
This 1B book is perfect to start off with (some may prefer to start with the 1A but I go straight to this one) and will help guide you with your early learning of the piano. Then as you complete the book, move on to Books 2, 3, 4 and so on. By about book 5 you're a competent piano player and may start to specialise in a genre of music (Classical, Pop, Jazz etc..) that you're keen to play.
Don't pay attention to it's 'Elsewhere Price' of $31 as that is just a rip off! They sell usually between $15-$20 online or in your brick and motor stores for about the same. So at $8.38 delivered, it is a bargain! I personally haven't bought from Fishpond before so can't comment on their shipping times and customer service however, a quick search of recent Fishpond deals, they don't seem to be all that great
Enjoy!
UPDATE - Price has been increased to $16.13 so I have expired the deal. You can get it cheaper through Amazon around the $14 price range delivered if anyone is still interested.
Comes up as $16.13?