I like the Spy Gear Car very basic and easy to build for a young engineer looking to show his girlfriend what he had built her.
I do like the idea of keeping the project simple for the young kids. Stack the modules onto the LEGO Build Board, which by the way if Arduino was adaptive enough they would enter into a contract with LEGO to produce Build Boards where Arduino Modules can be simply screwed onto the LEGO Build Board where other Build Boards with other Arduino Modules can then be snapped onto the main board, but I digress.
The more advanced kits would involve the builder learning how to incorporate the camera components into the Arduino's Processor.
I also have the idea of using the Spy Gear Car as a make shift boat. The tires would be hollow plastic filled with air that when the car went off road into the water the propeller would be turned on thus making two uses from the same vehicle for land and sea use.
I think the kids would have building their boat/car or the DUCK as it would be called so that when it came time to use the DUCK the fruits of their labor would be a triple reward.