Asking people to wash hands before touching my newborn?

My boyfriends mum and brother live just around the corner and smoke in their house and his brother shares custody of his son who they both smoke around; so I know they don't have a problem smoking around infants, and a few times have tried smoking around me whilst I'm pregnant so have left the room, my boyfriends mum rarely says two words to me unless it's about bump - who's 5 days over due! They try to say they don't smoke around my boyfriends nephew, but, I've seen them. When my baby's born I really do not want them picking him or her up or breathing on him or her afte smoking but they stink of smoke! I feel insecure about telling my boyfriend as his mum and I don't talk much anyways and they'll think I'm just making excuses for her not to be aroundthe baby? How do I say it without offending them? Or making my boyfriend feel uncomfortable? I don't want to take the baby into their house as I know theysmoke there and it's their choice but I know I'l have to constantly remind tem to wash their hands but I'm too shy! Is it rude to make a rule about smokers hand and breath? My own dad smokes however lives aboad but I can easily say wash your hands and take off your jacket if you smoked in it and have some gum!! Without offending him and probably my boyfriends brother too but when it comes to his mum I just feel so akward around anyway?! I'd like her to be more involved but she makes no effort with me, only the baby so I don't know how?!