Not being unreasonable.. I don't like anyone smoking near my kids. My SIL does smoke, but always away from the kids. When we are visiting, if mine follow, she will either go out the gate (and lock behind her), or put it out..

When my IL's were here for 3 months, towards the end, I saw MIL watching the kids in the sandpit, and she was smoking. I was furious. I spoke to DH and said that it isn't on, but he didn't say anything. As I don't have the best relationship with her, I asked FIL to tell her that it isn't on, and if she wants to smoke, I would prefer her to say that she doesn't want to watch the kids.