Uno + Monster Moto shield(s) for kids power wheels...

I’m trying to run a pair of monster moto shields in half bridge to give me double the amperage to hopefully safely run a pair of 12v motors. I’m struggling with getting the code and a proper setup to drive them. I’ve followed a bunch of examples and have been successful at getting the motors to move forward and backwards in a loop but unsuccessful getting them to be activated and controlled with a potentiometer and eventually a foot pedal. I’ve found example code that uses different motor drivers and only uses 2 pwm wires, no ina/inb to control fwd/reverse via the monster moto. Can anyone point me in a good direction?