Won't/can't give you marriage advice. What I can give you are some valid points for your argument against Mrs. Aberdeen.
She accepted you as a cigar smoker before. If it's an aspect of your personality, why should you HAVE to change now? Can you, or rather, would you ever even THINK or DARE to ask her to change an aspect of HER personality?
If you don't smoke around the kids, how can it harm them!?
Cigarettes and cigars are not the same. Cigarettes are made of trash tobacco and pesticide laden tobacco --ever hear of cigarette beetles!? No? I didn't think so. Nothing can live inside of cigarette tobacco. Cigarettes have chemicals added to them, cigars do not (but some cigar manufacturers do fumigate their tobacco for tobacco beetles).
Cigarette smoking is compulsive behavior, cigar smoking is a hobby. Ever hear of a forum for cigarette smokers? Or "Cigarette Aficionado"? Ever hear of discussions over the proper aging of cigarettes? The nuances of flavor in different cigarettes? No? Me either.
Regarding your kids not having a father when they grow up; How often do you smoke? If it's every day, you can compromise about cutting down (because maybe it is a habit if you're smoking that often). A few cigars (2-3) a week can't do very much harm over an extended period of time. Plus, she'll feel like she's gaining a lot of ground by reducing your cigar smoking by