If you ever have a significant claim, the insurance companies send out investigators to catch people who are trying to cheat. (I know this because my brother-in-law investigates insurance fraud for a living). If you get caught, you will be in BIG trouble.
I think you should let your son do this the right way. Make him pay for the difference in price since he's the one with the poor driving history. I know it's hard to make that stand, but this is what I think I would do.
Relax... I'll need some information first. Just the basic facts - can you show me where it hurts?