~ Younger ones doesn't have to gamble and with supervision from their parents, younger ones will not trying to playing gambling. If their parents can explain the effect of playing gambling at their ages and what will happens to people around them, their children will not trying to risks themselves by playing gambling. They will be careful when they are with their friends and always reminds each other not to playing gambling. They will tells many things about gambling, especially if their childrens can explain every details about the effect of playing gambling.
I think it's extremely hard to explain to young children of the age below 12 why is it bad for them to gamble. First off, you have to be an authority for your kids so that they were trusting your words. Secondly, they may simply don't get what you are talking about.
That will makes their friends will always carefully and will search for other entertainment. They can realizes that they don't have to follow other children who playing gambling because every children have their decision and if they are not playing gambling, that will be good for them.
The thing is that when kids want to gamble, it's not for entertainment for sure. They want to make money from it and money only is what interests them here. It's adults who can(and must) be gambling for entertainment purposes. That's why before you are an adult, you shouldn't gamble.