Nice job pwillard. That's way more than I am willing to do with that toy.
Carlcox89, are you planning to use the Analog pins? If so, you should disconnect pins 20 & 21, and connect 20 to a capacitor to Gnd.
The connection to 5V will be made internally if used, or you could use the internal 1.1V reference.
If the pin is hardwired to +5, you lose that option.