You know what can also traumatize a kid? If you cut of chickens head in front of them, or cut the throat of a ram in front of them. A lot of kids observe that, but that does not make them vegetarians, nor they did not grow up as a maniacs. Commenting on your post, it is a duty to keep on eye on emotions we show in front of them. That does not necessary has to be gambling related. Gamblers can show two main emotions, happiness or rage. Should we also not gamble in front of them to hide positive emotions? Or should we better teach them about emotions and behaviour?
Showing positive and negative feelings is healthiest part on the whole situation that gambler can do front of their kids, if they indeed choose to play in front of them.
Not showing emotions would implicate that losing or winning a fortune in gambling is normal behavior, and that can definitely be harming.
Kids idolize their parents and want to grow up like them. So witnessing their parents financial irresponsibility without having a clue why they do that would definitely make them copy it later subconsciously. And when they would lose, they would be completely lost and paralyzed by their feelings, meaning that those feeling wuould have control over them, because they are unequipped to deal with.
When talking about gambling and kids, people should focus on teaching and giving right experience, than focus on possible addiction or focus on negative emotions. If a person thinks only about bad, exactly that thing is going to happen.
Emotions is a good argument. We should not gamble in front of kids because we can show them negative emotions when we lose. But is gambling really the main thing here? If a person cant control emotions while gambling, he cant control emotions when did not gamble either. For example he can become aggressive when he is fired. What then, never told kids that you work? In this case better show yourself as a cool guy with cold head, and give someone else as an opposite example, just to show that gambling can be different, and that is why a kids should not gamble until he is an adult.