i dont think any gambler will intentionally want their kid to see them doing it. kids learn so fast and when they see their parent doing it they also want to try. its good to take caution and be very careful sometimes these kids might be watching their parents without them knowing and then they go to start practising behind them. one thing about children is that the like to practise what they see and if they see it constantly, it gives them confidence to want to try it.
I don't think any gambler have any intention of playing gambling in the presence of their children, but some people are very careless in the manner of how they do things which they can even forget themselves by playing gambling In the presence of their children. It is important for gambler to be careful and very conscious whenever they want to play gamble not to make mistakes of playing in the presence of their kids .
Children are very fast in learning and they pick interest to learn what will be a problem to their life in the future, gambling lifestyle can be a severe problem for kids if they are affected by gambling.
That because no parent wants their children to do the same thing namely gambling because it can ruin the future and affect the quality of learning as child but as you said there are some careless parents who gamble openly even in in front of their children because they become addicts and no longer care about the children or families they have accompanied.
I feel irritated with such people because they have gone too far by exposing their children to gambling activities and making it possible for their children to gamble too.
Apart from being very quick at learning children also have quite high level of curiosity which makes them more susceptible to gambling habits if they have tried it or know about it.
For this reason to always supervise and provide education to children so that they avoid gambling activities in any form rather than displaying gambling in front of children.