well they could do somethings simple for starters

police regularly pass through cafes etc especially in malls. So when they pass a starbucks for instance, 3/4 police go through and then go one by one and call them them all to come to them.

They give them a fine, tell them next time it will be 5X the size. What they can also do them is "name and shame" then, i believe this will have a large impact in Qatar where family matters.

Having them even with photos on the newspaper saying these "Individuals broke the anti-smoking law and damaged the health of our children", b4 you know it people will just stop and think twice.

Other option too is too increase cigarette prices, instead of 5/6 riyals make it 20 riyals, see what that will make!!!