You may want to look into some serious servo drivers if you want to run 12. there are many out there and some will be 3.3Volts but 5 volts is probably more common.
if you use a Logic Level Converter like the one made by Sparkfun (several companies produce them), you'll be OK (I'm about to try it tonight since I just received mine).
I use one like the one in this link but I paid a lot more :http://shop.kineteka.com/content/images/thumbs/0000678_logic_level_converter__125.jpeg.
Without any doubt though, you'll be safer using a 3.3V driver.
If you get one that operates at 5V and 3.3V, make sure you have it configured properly, they usually have a couple of pads that either need to be soldered or cut separate.