In article , snipped-for-privacy@hotmail.com spouted forth into uk.rec.cars.modifications...
You could have a look at Retro cars. Older cars upto and including Mid eighties. So you will find plenty to entertain yourself (AMG merc powered MG ZB Magnette, and MK1/2 escorts etc) and remind you of your youth, plus a few Peugoet 205/Nova/Golf/R5 GTT type cars in there.
Not so much the big body kit variety, more the handling/tuning/performance type stuff, but nothing wrong teaching him to make a car use it's maximum standard power better, and making it use it safely and efficiently, before going on to building up a solid engine and then when he is 17 or so moving on the Max Power stuff and putting a decent kit on it then. Remember when he is 9 years old, what he likes body kit wise now, will be very dated when he actually gets to drive the thing. Better to build a solid reliable decent solid looking car now and tart tart it up later than put together a huge tea tray with the handling capabilities of an oil tanker on ball bearings.