A lot of efforts are made to prevent kids from getting closer to gambling and knowing about gambling but I think the best thing to do right now is to sensitize the society which has already been eaten deeply through gambling. Adults who are going hard and crazy everyday should be controlled before going after tv channels and social media channels that users ad to promote gambling. Again most of the children get more knowledge from their friends and family members who are real gambling addicts they need to also be protected from such persons if they must stay away from gambling.
I would actually love to see this idea in reality but that may not be possible because everybody has the right to advertise there gambling platform and besides if the country is a gambling friendly they can actually do it the way they like by talking about it in media but since all the parents is aware of the country being acceptable in gambling they should give themselves a duty of a parental restriction of there children in gambling because if they only want a law to be enforced by government to guide the teenagers from gambling they might be relinquishing there duty to there children.
It's still going to be on the side of the parents/guardians to take care of their love ones, like what you said, if the country is free for types of business, there's no way that it can avoid to see ads about gambling to the point that it can direct viewers and followers to follow them in their journey towards gambling, there's no stopping as those kinds of business are bringing generated income for the government in terms of taxations especially those undergrounds transactions.
The only place parents wouldn't have to think about their children in regards to gambling is when the country they based is the type that is against gambling so that there isn't how any child will thought of it or even leant about the existence because there will not be anybody to mention or even the gambling platform accepting the person and in social media they might not see anything related to gambling since all their friends will be only those that based on the same side they are, so with this the parents worries will be on other things but definitely will not be in betting.