Looking at the Adafruit link,
this shield looks like it has everything you need. 2 servo ports, those would be your brushless ones, and 4 DC outputs, so you can run either 4 DC motors, 2 stepper motors, or one stepper motor and 1/2 DC motors. It also has 6 analog input ports, and it looks like 14 digital IO (not sure which ones are in, out, or bidirectional). As long as you're on the shy side of that "1-2 brushless" quantity, you'll be fine. I'm guessing the servo would have been for Ackermann steering? Anyway, good luck.