Then be sure to keep your children away from Niacin, tomatoes, potatoes, eggplants and the like.
All You Need To Know About Nicotine
Nicotine in the diet
Nicotine is a normal part of the diet and everyone tests positive for it. In all of the large-scale clinical surveys where hundreds of subjects were tested, no person has ever tested negative for nicotine 
Nicotine is a normal ingredient in vegetables and everyone consumes it (13]
Nicotine is an active alkaloid  and an active part of the diet  - removing it has negative consequences for some , and supplementing it has benefits for some 
Its sister compound nicotinic acid, co-located in the same plants and with several benefits in common with nicotine, has been allocated vitamin status as Vitamin B3 (although the researchers had to invent a new name for it in order to get it accepted) 
You feed your baby nicotine in her mashed-up vegetables, and no corrupted medic has ever dared to claim this is a bad idea since nicotine is so closely associated with the B vitamin group that a nutritional deficiency would almost certainly be created if an attempt were made to try and artificially exclude any active ingredient such as nicotine .
But the question is about children vaping, which would be a bad idea for them to do, unless they had a cigarette in hand and about to light up. Kids will do what kids want to do when nobody is watching. I think most people would prefer they did neither (smoke or vape). Looking at the past century before e-cigs, how many of us could have made a better choice if we had the option.
Its the amount of nicotine we are discussing not trace amounts one may find in food. is 3mg nic juice going to have an affect? probably not. is 24mg? quite possibly. and im just not one who buys into the better of two evils argument. so kids are going to drink, so lets be ok with them getting it as long as its beer and not hard liquer? they shouldnt be doing either. period. there are so many things that have adverse affects on the brain during development. and whether or not kids "will do what kids want to do" is very much related to the involvement of the parents. people should have to pass more than a physical exam to become parents. and on another note, us showing any sort of approval for kids vaping is just going to fuel the anti-ecig agenda. just last night i was reading a post from a moderator saying they saw posts from this very forum quoted on anti ecig websites. i for one love vaping and dont want something like us having a lackadaisical attitude about under age vaping to contribute to the looming strict regulations