i know you've gotten lots of responses, but i'm going to add to it anyways :)
just a couple words to begin: GET OFF IT, GIRL!!! ok, now that that's out, lets go forward.
i wonder - you said that 'otherwise we are a happy family'. so, what is it about his smoking? it's not really about his health. many many many people live to ripe old ages smoking their whole lives. that may be the public version of why you want him to quit, but if i'd have my best guess, i'd bet that it's your 'litmus test' as to how much he REALLY loves you. so, it's completely about how much control you have. if he is a good husband, doensn't carouse around, doens't drink, is good to your children and you, supports you as a good husband should, i suggest you leave him alone. quit the nagging (YES, IT'S NAGGING!!), quit filling his prescriptions, quit making appointments for 'us'. just quit. quit with the control. admit that you do not have total control over anyone but yourself. if you don't you just might find yourself a single mom w/ your children visiting their dad.
your husband sounds like such a sweet accomodating giving man that he's telling you that he'll 'do it for you', but he's also told you that he loves it too much. it's a horribly hard thing to give up. my sister, who is medically fragile, also smokes even to the detriment of her health, but she also loves it and cannot/will not quit. she's tried, even quit for a year, but the urge is just too great. she also has 2 kids, and even for them she can't/hasn't quit. and she KNOWS how it's detrimental to her health.
so , i suggest you just get off it. leave him alone. if you want a happy loving marriage, just admit that he's got this one thing that is HIS. stinks, but leave it to him. i mean geeze, he smokes and comes in a cleans up afterwards. how much more do you want from him? ask for too much and it'll come back to bite you. people have to have control over their own lives or their going to resent the controller. if you browbeat him into eternity, he may pay you back by finding someone that can love him as he is.
love him for what he gives you - which is a LOT, girl. many many ladies out there would give their eye teeth for someone as sweet and accomodating as he is. i've found mine (who spends far too much time on the couch , but otherwise is a great guy), so you can see that there is NOBODY that is perfect.. if you demand perfection, no one can attain that level and will eventually quit trying.
good luck w/ 'your' problem ;) i think it's just that, not his.