Xbees want 3.3V, although if there's a shield involved that it plugs into, that might regulate the 5V you supply it.
Other than that, there's nothing in your diagram that shows anything that "should" damage the Arduino. Perhaps if something is a short to ground and you're trying to drive it high, you will end up overloading some pins. It should be safe to add 220 Ohm through 1 kOhm resistors between the Arduino and the LCD inputs, for example, to prevent that being a problem. (That's an approach taken on the Ruggeduino, to protect it from blowing up when wrong-wiring -- if you do a lot of experiments, you might want to get one.)
Also, the difference between 12V and 11V in the Vin should not matter. If the video thingie really wants 12V, just make sure your output power supply provides 12V. The upper limit is 20V, so you have plenty of headroom. The reason they "recommend" 12V is likely that the regulator will run warmer the higher the input voltage is, and you might burn yourself on it if there's a lot of load and the input voltage is high. (Or maybe they don't have a big enough copper pour to heat sink it -- one of the many problems of linear regulators...)