Uptake by children is of course something that public health are keeping a very close eye on. It is covered in the PHE report here:
Youth:Regular EC use among youth is rare with around 2% using at least monthly and 0.5% weekly. EC use among young people remains lower than among adults: a minority of British youth report having tried EC (~13%). Whilst there was some experimentation with EC among never smoking youth, prevalence of use (at least monthly) among never smokers is 0.3% or less.
Overall, the adult and youth data suggest that, despite some experimentation with EC among never smokers, EC are attracting few people who have never smoked into regular use.
Trends in EC use and smoking: Since EC were introduced to the market, cigarette smoking among adults and youth has declined. In adults, overall nicotine use has also declined (not assessed for youth). These findings, to date, suggest that the advent of EC is not undermining, and may even be contributing to, the long-term decline in cigarette smoking.
Simply put, vaping, even with nicotine, shows little sign of being addictive in the same way as smoking. This shouldn't be a surprise. It has been known for some time that nicotine on its own, e.g. in NRT, is far less addictive than the 4-5000 interacting chemicals in cigarette smoke.
The study talked about on the Channel 4 site shows a correlation between kids who try vaping and kids who try smoking or drinking. No shit sherlock - risk-taking youths take more risks! The supposed 'gateway effect' is discussed at some length in the PHE report here. There's also a good blog post here which discusses the problems with gateway theories.