OK so the page calls for a 5V power supply. So you would need a 5V regulator. Now to power that regulator you need a voltage of above 7 volts.
Servos should not be powered from the regulator but from a regular , unregulated 6V source , but sensors can be powered from either regulated or unregulated power , doesn't matter
My guess is the board will run at 6V , since most microcontrollers are meant to run from between 4.8 and 6 volts, I run my PIC micros @ 6V all the time.
If you are scared then take a 6V battery and attach a diode to it (which usually drops the voltage by 1 volt as a side effect ) and then connect the diode end to the microcontroller .