I believe, there will be stages that one would reach in life, it will be okay to introduce a certain thing into their life despite their age as long as they have reached a certain age bracket.
Since gambling is risky and involves money, letting the young ones learn how to gamble responsibly is ideal, but what effects are doing that since they can't provide for themselves still yet, but depend solely on their parents for feeding and clothing. Having them, know about gambling at an early stage, can change their thinking from studying more to gambling more since they can make little or no more in a week or month.