From my personal playing experience + imagining what today's kids might like / find acceptable, I would support "Bomb Jack" (played using a joystick, though, not the keyboard) and I would add "Jumping Jack" (played using the keyboard), both having fantastic gameplay which I think makes their "poor" graphics irrelevent.
In a similar vein, perhaps "Frogger" could do the trick, too? Plus one of these games (I can't remember the name right now, I think there must have been various versions) where you have a moving platform at the bottom and there is a ball or something which bounces off it and goes up and destroys blocks up there, and then comes back downwards, and you have to be there at the right place to make it bounce back up again.
Another of my favourites of the 1980s, with a fantastic gameplay for me, was "Paperboy" (or "Paper Boy", I can't remember the spelling off the top of my head). However, I'm not sure if the graphics would not put them off, taking today's standards into account.
Another thought (slightly blasphemous!) would be to use some of the PC remakes of the 1980s classics. They wouldn't convey the full flavour of the originals (loading from tape, etc.), but they might showcase some of the old games with graphics and sound more accessible to the young generation...
Edited by jetsetdanny, 11 August 2017 - 08:39 PM.