Following Robot Guidance

So long story short, I will give a brief description of my project(I know there's similar, I would like guidance), and the parts that I'm ordering, guide me I'f theres an easier path or wrong procedures or wrong parts, most importantly motors and motor driver.

My project is an ultrasonic following robot.The robot will send out a pulse request(xbee), then begin timing. The receiver you wear gets the request(xbee) and sends out a pulse(Ping))).
The robot has 2 sonar sensors. It times which sensor gets the signal first, difference between, and uses this to calculate the direction and drive.

So using Ping)) ultrasonic waves (3 of them).. Turning 2 into receiver and 1 transmitter by ripping them out.

Xbee wireless, for pulsing the transmitter from robot to transmitter. works good with Arduino?

Motor kit 7.2 VDC motors., Can I use this with the SN754410 motor driver? (most important)

Good battery for the project? 7.2V / 2800 mAH Ni-MH Rechargeable Battery