Maybe it would be better if stepper motors were used in the drawing robot. This is because the encoder motors would be adequately covered by the other projects, students would be introduced to stepper motors and the stepper motors would produce a far better result. The MKRMotor Carrier does support steppers.
I'm trying to get my daughter interested in STEM (showing not telling), and she sees the noisy result and is really not impressed.
These projects could be a great way to sell engineering to people thinking about engineering in high school but they have to be somewhat impressive. (I have not done the other projects yet)
However nothing really would prevent some one (such as myself) from doing this anyway and that is part of engineering. All that would really be needed is to 3d print a mounting bracket.....