In my opinion, even though i'm not a parent, you should try not to hide stuff from and lie to your kids. You shouldn't hide the fact that you smoke just as you shouldn't lie about sex and other subjects that are considered 'inappropriate' for young kids. Maybe it's best not to smoke in front of them, but don't hide the fact that you are smoking - if you do lie about smoking and lie about how you feel about smoking then the chances are that your child will find it awkward and uncomfortable talking to you about smoking when the time comes. Maybe you could let them know that smoking isn't a bad thing, but that they can't do it until they're old enough just like they can't have cigarettes or alcohol until they're old enough. That way they'll grow up thinking that smoking isn't as taboo and unmentionable as most people think, and hopefully you'll find that they'll listen to you more when you finally talk to them about smoking because you have their trust due to your honesty. I dunno, I might be wrong - like I said I don't have kids, but that's the way I see it.. then again, I am pretty high.