As the father of two boys, 8 & 3, and the expectant father of twins, I have been reassured enough through the limited studies out there that what I'm exhaling isn't dangerous to my family. Like others have mentioned, I wouldn't feel comfortable blowing the vapor in any of their faces, but who would?
I try to be discreet as possible when vaping in the same room as them, only because I'd prefer not to make it seem like a desireable thing to do. Both of my boys know I used to smoke cigarettes and they know that my various mods, atties, etc., are the "medicine" I'm using to quit smoking. That's all I want them to know. I also make sure to keep all of my vape gear and liquids locked up and out of sight when I'm not using them.