Funny but I'm building a kit for my 30+ year old brother-in-law. A few years back I had to fix EVERYTHING for my sister, but the guy's coming along pretty well. Last Sunday we replaced the upper and lower ball joints in his '99 Ranger, and he was obviously behind the curve compared to me but he caught on fast and was a great second set of hands.
I know the 'buy quality, buy once' mantra, but I went with some pieces I found at Lowe's that they were discontinuing. 1/4 drive ratchet and socket sets were $2.80, and a 1/2" metric set with a socket wrench was $11. He has a Taiwan set of 3/8 stuff already, so that should cover him pretty well. I have a pile of Craftsman screwdrivers, pliers, wrenches and the like to fill out the rest.
I got my first carry box at 11, and I still have the hammer, socket wrench and most of the sockets that I got the same Christmas. I got a lot more tools when dad died two years later, but I still knew what was mine because his were 20 years older. The starter stuff was one of the best gifts I've ever gotten, and I certainly appreciated it. The next year I got a cordless drill and screwdriver combo (this was like 1988, so that was impressive stuff) and was floored.
My family still has the muscle cars we owned then, and I've worked on all sorts of stuff over the years. You could also think of adding some homeowner type tools like a pipe wrench or a claw hammer as those will be useful for the rest of his life.