I've been using Hackasaurus to teach kids for a while now (as part of a project I'm working on for the Mozilla Foundation, and also through Girls Learning Code, the tech camp I run for 9- to 13-year old girls), and they just love it.

See some of the projects the girls created using Hackasaurus at our Girls Learning Code March Break camp here: http://heatherpayne.ca/the-girls-learning-code-projects