Preator wrote:And with 4 AA batteries, will I be able to power the 2 motors?
Yup. I used to teach robotics with Arduino and the Magician chassis. I used two of these packs (4 x AA) per robot. One pack powered the Arduino. The second pack powered the motors. You can get about 4 or 5 hours of roboty goodness from a fresh set of motor batteries.
Using two supplies in this way is important. If there was only one pack then after a while the Arduino would brown-out and reset when the motors started. With a separate pack powering the Arduino, it can keep running even when the motor batteries are low. The advantage of this is that the Arduino can detect this condition and flash an LED or something to show the motor batteries should be replaced.
It's even more important for a Pi. You do not want your Pi browning-out and corrupting its SD card when the motors are turned on.