You are right, there is no need to hide anything from children this days, one day you will be shocked to find out that they knew about gambling already, someone close to them might have influence them.
You are right about this. We need to educate our children about gambling. But it should be on a very basic level, I believe. If you go into deep while making them understand about it, then it will grow curiosity in the mind of the child. Then they will start exploring about it more by themselves and will be eagerly waiting to try gambling. Hence, just the basic knowledge about the definition and the merits and demerits of gambling can really help the children to understand the things better.