A little Xylene (Goof-Off) quickly applied should lift it off without harming the inks assuming there is a coating on it. Also, you can try using a black DRY-ERASE (Expo, Expo2) marker. Dry Erase will often lift permanent marker marks right off. Go over them with dry-erase pen, let dry a few seconds, then erase. It works to remove accidental permanent marker from whiteboards.
Just picked up a Battlezone from a guy that has 3 young kids.. The right side of the machine was pushed up next to another arcade, so it was safe from attack.. The left side was open to the room.. They had crayon pictures drawn all over the left side.. I was lucky it wasnt a sharpie, it did clean up...