I started collections for both my kids before they were born. Nothing special just different kinds when I would find them at a good price. They have always been exposed to knives and their uses and have been allowed to help out in a very supervised environment. They have also from time to time been allowed to look at an study their collections and see how different knives work, opening and closing, cleaning, and care. By 9 or 10 they were allowed to really use their knives to carve with and experiment with, again under supervision. They have always been taught that there is no room for error when it comes to safety and care of knives, horseplay has never been allowed with any knife for any reason. My son turns 18 in a few days and is much safer with knives than I ever was at his age he owns many knives and even a couple of swords which stay on the wall. My daughter turns 12 in a little under a month, and she doesn't know it yet but one of the things she will be getting is her collection, having proved herself to a careful and safe with a few small knives that she has been allowed to keep in her possession over the last couple of years.

I think a SAK is a good first choice, they even have one called My First Knife, which has a slightly more rounded point. I also would make sure that a first knife choice does not have a locking blade, I think a non-locking folder helps a beginner learn the fundamentals without the false safety a lock can provide.

Good luck with your son, it is truly a special time when you can begin to pass on the knowledge that leads to a mature and responsible adult.