Please help!!!!

i need help for a little mini workshop in robotics using the arduino board to high school students but we are having problems defining the minimun stuff for each kit. the main idea is that the kit does not cost more than 115 US$ including the board and taxes. The funny part is that we are informatics (or computer sience engeniers) and we have a small knowledge in electronics but decent knowledge in resolving problem with prefabricated robots.

by now i have: the arduino board, usb cables, buttons, touch sensors, leds, Phototransistors, a small breadbord all by US$ 60.

we think that we would also need, L297 MOTOR DRIVER, ULN2003A driver (by reading the tutorials:P), and obviously some small motors (it can be the TAMIYA's Dual Motor GearBox).

Almost all the stuff are in please help us. wait for news ;)

i forgot that in sparkfun they have this motor drivers

thanks to all.