Context is FIL chain smokes to the extent that DH won't take the DC to their house as they smoke indoors so it's very strong smelling.
When inlaws visit FIL goes on the front garden to smoke. Now it's summer the DC are mostly in the rear garden when they visit so FIL will sit chain smoking while DC are playing.
Is it unreasonable to ask him to go onto the front away from DC to smoke still? I haven't suggested this to DH (he'd be the one who asked him to) as I didn't know if I was being U. It's not a big garden but my issue is when he visits indoors he can manage 15-20 minutes without smoking breaks but when we are outdoors he smokes one after the other so we all sit breathing it in.