Stepper motors are awful. Heavy and power-hungry. Use DC motors in your
robot.

The 16C84 has no A/D or D/A. The "7" series has A/D but no D/A. The parts
are available in windowed versions eraseable with a UV eraser. In a simple
robot you should not need A/D, stick with your 16C84 for the students...

my 2 cents :-)

-Bob