Tank on Tank would be great game for this. I actually made that module for Mark Walker.
As for timing, to teach VASSAL we'd really have to do it live but it could all be done through the chat function.
I can play at lunchtime, 12 to 1 pm EST, or after work. (I should really be writing an engineering design note for an FEA I did on Dipole magnets right now, but it's a bit boring..)