Parents are not just teachers to their children but their children sees them as their role model whom they are looking up to copy whatever they see their parents doing. Gambling should be done privately and that's why the online casinos are there for us to keep thing privately without anyone seeing you gambling.
Even if I gamble several times a week on my mobile, I should do it secretly or when children are sleeping? I think you are creating gambling into a monster, an activity that does harm to everyone, something that is really bad. To bad that your suggest wont work. Ok, your child wont see you gambling, but for instance, when you walk on the street or watch TV, they see gambling billboard or advertisement. What are you going to do if your child ask what is that? Say no-no, that is bad, dont look, listen or even think about trying. Think that is going to help? You believe that your child will never find out or hear what is gambling, except at home? Even in movies, cartoon, games, there will be moments when someone plays lottery and wins. That gambling. The way character spends money won is already a stimulation for your child to gamble.
Speaking about gambling and children, I think that parents role is not to hide gambling activity, but be more open and instead give all the information, and later monitor children activity. You say that parents must be a "role model", someone to loop up to, someone children want to be. That is correct, but parents must be also someone who children respect. Someone with a reputation. If parents say that their children should not try gambling until the turn 18, and give examples and explanations why, then children must listen to that.