The motor driver you've chosen would be a bad choice for a 24 V power supply, because 24 V is the absolute upper limit on the motor supply voltage for that driver. You need to give yourself a safety margin. Also note that lead-acid batteries, when fully charged, have significantly higher voltages than nominal (a "12 V" battery will carry about 14 V at full charge). One option is to use lower battery voltage.
If you insist on using 24 V, there are a couple of motor drivers at Pololu that can tolerate higher voltages: Pololu - Brushed DC Motor Drivers If you buy from them, you get clear instructions on how to wire up and control the driver, plus excellent engineering support via their user forum.
Finally, you really need to know the maximum current draw of the motors.