I don't understand whether children should be gambling in front of them but I have seen little the boys in my area gambling through mobiles. However, the parents of those who gambled through mobile were not addicted to gambling, but their children were addicted to gambling. Even though their parents never gambled in front of those children, they still learned to gamble. They are hated by the family for such activities.
That's because of the surroundings and the influence of their friends. It's really because of how they've managed to see gambling through mobiles from their friends.
If it's not because of their friends, they won't gamble just like their parents. But even the surroundings is out of scope of the parents, they still need to check their kids from time to time and what they're doing with their gadgets.