I do know that I will need a separated power supply to run the servos properly. But, for a fast presentation, do you guys think that a 9v ordinary alkaline battery will make? If so, how long? I am using those mini 9g servos!
Well you can make a better conclusion based on a measurement. Run one of the motors at 5vdc at full speed and under whatever mechanical load they will be subjected to and measure the current draw. If both servos are to be running at the same time then double that measured value. When you have that number then we can talk some more.
If you want my gut opinion your wasting your time planning on using a 9vdc battery to power two servos. Get a 4 alkaline AA battery cell holder and plan on powering your servos separately with that, saving the 9 volt to just power the arduino board.