1. At what age will you allow your child to start gambling? that is if you will even allow for that at all?
This question sounds strange like why would you even want your child or children to gamble in the first place? It is good for your children to know about gambling so that they won't be misled by friends or peer groups outside but allowing them to play gamble is very bad at a very young and tender age. Gambling is not bad but never allow your children to play gamble because if they do you will find out that they will be devoting most of their time in gambling and disregard other life objectives because they will think it is an easy way to make quick wealth if they play consistently.
I assume you didn't understand the question the OP asked. His use of children in the question doesn't mean underaged children but offspring who have reached gambling age. Your child will always be called your child regardless of his age. Of course, the majority of parents would not want to introduce gambling to their children at a tender age because it violates the law of many countries which the gambling age is generally 18 years and above. OP was trying to know at what age (within gambling age), you would want your children to start gambling.
Just as you stated it is important to expose your children to gambling so that they would be able to gain proper understanding instead of getting wrong information from social media and peer groups. I prefer that my children choose other forms of entertainment than gambling. They used to choose music, sports, or writing and forget gambling because its addictive tendencies are harmful.