How do you tell someone this.

How do you tell your boyfriends 60 year old, bed ridden father that you don't want him smoking around your kids anymore. Both my kids have allergies and the smoking just makes it worse. I don't smoke and it at times is too much for me. The headaches, nose bleeds, even sinus infections. I've had two sinus infections since we got together last year and I feel another coming. I'm due at the end of September and I don't want my baby around the smoke. Our house is small, so literally within seconds of him lighting his cigarette, I can smell it on the other side of the house in my room. Idk what to do. But it's really starting to bother me because my daughter is having nose bleeds again. And her eyes have dark circles under them again. She gets them when her allergies flare. My baby boy has a heart murmur and I don't want the cigarettes to make it worse. I'm just like. Idk what do do.