i don't have children yet, but many of my friends do, and i choose not to vape in front of them whenever possible.
i have two friends in particular who both smoke in front of their 3-year old, but only outdoors on the patio. i brought my eGo and some juices out one time and the little girl asked "what's that?" i didn't want her getting any ideas that it was candy liquid or anything like that, so i told her "it's my special medicine that my doctor gave me to quit smoking, but you should never touch it or else it will make you very sick." it was funny, because later that night, i offered one of my friends a few puffs and their daughter says "no mommy! it'll make you very sick!". haha, i thought that was cute. but at least now she knows what it looks like and won't touch it if i get careless and leave it around the house somewhere. though i'm especially careful about that.
i have another friend who has two little girls, maybe 2 and 4, and him and i were sitting at a local restaurant not long ago having a bite to eat and kicking back a few brews. he knows what my e-cig is and the restaurant knew what it was and said it was fine that i used it inside (it's a non-smoking establishment). his wife showed up with the kids at some point and i put my eGo away. my friend said "nah man, it's cool, it's not smoke or anything". i still felt weird about it and opted to step outside to use it from then on. although i didn't feel weird at all about drinking beer in front of them, kind of hypocritical i guess.
i just feel like vaping is a better alternative to smoking for me, yet still not something a non-smoking child should be witnessing or even admiring, whether it's safe for them to be around or not.