Although the trading is very risky but one thing should be remember that by tolerating failure and taking risk we can go ahead but if we don't face such situations then how we will learn. I think that you should engage your children in such activities because in few years he will just make experience and will do better by experiencing through gain and loss. If there is nothing to do and you have a firm believe that your child will engage in trading in future then surely its a right time to make his concept clear about trading. He will get some knowledge from you and some knowledge will be easy for him because of facing gain and loss situations.