Meet the Cherokey Robot: a 4WD robot building kit for Arduino that teaches you electronics through hands-on experience. This wheeled robot comes with IR sensors, an ultrasonic sensor, and Romeo microcontroller. By playing around with this robot, you will learn more about Bluetooth, sensors, and robots in general.
This robot has an expansion plate board for connecting a 9v servo or a standard servo in two different locations. It has max payload of 500g. You can find out more about it here.