I deal with that all the time when I come back from college. I've become good at just acting normal when I want to around them. Also add to the fact they smoked in their younger years they really don't care that much that I do it. The only way I could see them caring is if I drive high, which I don't do normally, I wait til I start to come down or atleast get my head somewhat back into things.

They probably won't be able to tell unless you look at them and they see your eyes are bloodshot. Get some visine and wait 5-10 mins before going around them, your eyes should be better by then.