Smoking around the baby

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I'm 33 weeks and I sort of have a problem. There are people in our lives who not only smoke, but smoke to excess in their homes. Namely my stepdad smokes a lot in his and my moms house. I don't plan on telling him he can't smoke in his home, but I also don't want to take the baby to a house full of smoke. My MIL also smokes, but lives 800 miles away and I suspect she would stay with my husband and I when the baby comes. She already smokes outside, but I also don't necessarily want someone cuddling on the baby when the smell like smoke either. Am I wrong? My husband agrees with me, but how do we tell these people that we don't want their habit to effect the baby?