There are many ways can cause someone convinced to become a gambler, not only because of old people or their parents.
If he live in a country where gambling is legal, he can see the gambling ads almost everywhere.
Social medias, articles, or any sites sometime accept gambling promotion, if not the user can promote it by themselves.
Friends, colleagues etc also can introduce someone to gamble.
Everything has a risk, including "life".
Talking about kids, they'll have multiple factors, in future, that'll lead them to gambling, but they can be stopped or trained not to fall for those factors. You can't say that all the kids or adults in gambling legalized countries would venture into gambling, due to ads. When we train kids the right way, it helps kids to follow the right route of life. So, parents need to help the government in the fight for gambling addiction in the life of growing kids. If nothing is been done, they'll go through a difficult time, growing up and won't be able to resist the ads like you said. Hence, in the case of OP and his kids or younger siblings, it's important to teach or help them avoid these people while still toddlers. And, they've been numerous contributions on what should be done with the adults, who tend to alter the future of these kids or influence them in the wrong way. In all the responses, risk is also involved. Since we can't determine the relationship between Op and his elderly neighbors or friends. Which results to the kids, listening to their conversations. When these kids are allowed to sit or play around environs where gambling is constantly a topic of the day, it'll affect their mental health and victimize them into falling for gambling adverts. They all fall in same category as kids that watch their dads gamble or follow them to gambling rooms or shops.