Teaching programming at GCSE level (OCR Cambridge Nationals Programming unit)

IT Budget money to spend!!

I would like to teach programming to pupils next year and I am looking for an suitable teaching software package to introduce this in an easy, step by step guide to programming.

I would like to base this on the Google android Apps development platform which allow Apps to be created for android mobile phones. I know there are lots of free Google resources and web sites out there . But I am specifically after a teaching resource (unit of work) online “front end” to the main Google App development that will be aimed at introducing this to pupils. And easier to use and follow than the Google App inventor tutorials etc.

Can anyone recommend a package?

Thanks for your advice.