What do u think about the arduino motor shield i mentioned above
That shield may be marginal for you. It handles your voltage and up to 2A per motor. Your stall current is something over 3A so you will need to monitor the current via the analog sensors and shut down if it goes over the 2A limit. Just read the datasheet carefully as braking current over 2A appears to fry the chip. Also note request for flyback diodes as in figure 8 of the datasheet. If you are careful it will LIKELY work. No guarantees as you have not fully characterized the motor parameters.
Well in that case i might go with another shield i have been informed should work but i will first get a battery and finalize the parameters