The kids name is not Steve or Mark Ritchie is it? (Just Joking Here, ).
Warning! The following suggestions must be used with extreme care. Warning!
Okay You tried Novus, Do have any Car Detailer friends? They might give you a small amount of a polish/compound for Clear Coat Paint. It has to be for Clear Coat Paint. Those harsh rubbing compounds that contain grit, I would avoid using them. Or use as a last resort.
There is that OXY CLEAN, it is suppose to remove most ink. Get the powder OXY Clean mix some up a small batch. With a rag, work it onto the inked area. Be careful, it does bleach many surfaces. If you see any colour change wipe or dab it off carefully. Can you use both the Oxy Clean and the Magic Eraser, I have never tried this on a pinball playfield before. I've used the Oxy on an ink stain but it was on fabric. The ink came right out, with success.
If the damage was caused by a ball point pen, there could be a depression still remaining in the wood. Even though you have removed the ink colour.
Good Luck.