I very agree with you by" Unless you plan to invest small amounts over a long period of time ( buying when low and high )"
but it is not sure what is the next crash, what will cash the market ,and when?
no one can make it sure, but we can wait all the time ,but we can invest small amounts, and plan keep it a long time ,When you invest in a small portion, you will remain sharp and observant about it,I really think you can give your son a small sum of money to try and make mistakes,If his investment fails, I believe it will also become his experience and a wealth in his life,Keep him alert to the market as soon as possible, and as much as possible,