Giving them a warning is fine but that's where the kid's curiosity about what's gambling is all about starts.
I agree, but the kids will try to search what is gambling, and if they find it by coincidence, I think they will try to play. The kids will have a big curiosity about something that they don't know, and they will search more and more until they found it.
If I'm a kid, a 6 or 7-year-old boy, always seeing an active gambling community around, I will ask myself, why we kids aren't allowed to play gambling by our parents or seniors even it was allowed on our Law. I saw other kids doing gambling but they aren't stopping. Gambling operators will allow these kids to gamble since it's legal and it's not their responsibility to stop these kids if they really like to play.
I guess they will not ask about that, but they will search what gambling is, and if they see that playing gambling is excited, they will try to play. That is what the kids do, but some kids will ask about something that they don't know as that is what my nephew asked me about some games that his brother played on his computer.
So I'm thinking, why not just turned this kid's gambling activity into something resourceful. Let them gamble instead and help them enhanced how to analyze things in a certain situation while doing gambling.
I think that is a job for the parents or adult people around the kids to tells about gambling, what is the advantage or disadvantage so they know why they should not trying to playing gambling. I think if we can say or teach about a good thing and also tell about the wrong side of something, they will feel that they should not do that bad thing. Perhaps, it's like mental training or planting into the subconscious about something that can give bad things.