The L298N has a voltage drop of between 1.8 and 3.2 volts @ 1A, so you're going to need more than 3V drive to the L298N motor supply anyway. There's not much point in using a regulator for the motor supply. I would use 3 or 4 AA cells and no regulator to provide power for the motors, and a separate supply for the Arduino.
@James C4S: using only 2xAA is not a viabile option because the 2 batteries don't provide the necessary current to drive the motors... (tried this option:D )
I measured the Vout for all outputs and I get 3.10 - 3.20 V (@ 3.2 ~ 3.3V input) so as far as the measurement went I didn't notice any voltage drop.So... is there something that I'm missing ?
You must have been measuring the output with little or no load. Try measuring the output with the motor connected, and measure it directly across the motor terminals (i.e. between the two H-bridge outputs).Running a motor above its nominal voltage under light load will not harm it. What you need to avoid is prolonged running with the motor stalled or under heavy load, because this will burn out the motor or the H-bridge.