I was summing up all the I/O I'd likely need for the car and it looks like I'm going to be a bit short, 2 for each of the main motors, 4 for the lights, 5 for the Furby's motor control (3 out, 2 in) and then perhaps some for micro-switches and light sensors.
Given that we've got two Edisons then the obvious solution is to use a second one to control my Furby driver and then use i2c, serial, wifi or Bluetooth to communicate between them.
My main concern is that the breakout board connects directly up to the Edison so I'm thinking about options to drive hardware from that. The two key issues are current and voltage. The Edison's GPIO is 1.8v and can supply about 3mA.
http://www.intel.com/content/dam/support/us/en/documents/edison/sb/edison-module_HG_331189.pdf
In the scrap box, I've got some level shifters, some ULN2003 Darlington drivers and some 4n35 opto-couplers to choose from.
