You are not getting my point, or you are taking things to litterally. I am not saying that anyone here wants to be GOD to their kids, its simply a matter of fact that they perceive you as such until they can think rationally. Think about how you felt about your parents when you were a youngster, you likely did not see their flaws as flaws. You are your childs whole reason for existence when they are young. You are the one(or two) beings that he/she "knows" will always be there to protect him/her, and whatever you say and do is true and good to him/her. While they are young they have the same faith in you that someone might have in their "GOD", so obviously you are not their GOD, but you may as well be.
I agree that education is the best way to approach the situation, and you should always tell your kids the truth. I have never suggested hiding anything from them, just that it is inappropriate to do certain things openly in their presence. There is nothing wrong with them knowing that mom or dad is having a smoke or vape, and that you just dont want them around it because it is for adults, hence the reason you do it outside or in another room. Vaping is not the most horrible thing in the world to do in an enclosed environment with kids, but it is akin to smoking(like it or not), and smoking is a pretty horrible thing to subject your children to for many reasons.
Lets keep in mind that there is concentrated nicotine in your PV, so I hope your equipment and liquid is well secured. If a child sees you vaping and decides he/she will try it when you arent looking there is a chance that something very bad could happen.
Is there a point at which kids are capable of thinking for themselves, of course. Once someone is old enough that you allow them to go places by themselves without adult supervision they are hardly kids instead they are adolescents, and a different set of rules apply there.