Have fun with Science & Technology for Kids of all ages
For a through description the Arduino, it is recommended to follow the link below. It will describe an entry level to the control world with loads of applications.
The sessions start with an introduction for first timers to project oriented sessions where complete projects are assembled and achieve an operational state.
The Raspberry is a single board computer with the ability to connect directly with inputs and outputs directly. For best understanding of the Raspberry Pi the link below will provide an in depth description.