According to this article in Time, Yale researchers have said that one in four high schoolers who use electronic cigarettes are inhaling vapors via an alternative technique known as "dripping."
"Dripping," is where e-cigarette users inhale vapors manually by dripping e-liquids directly onto the device's battery-powered heating coils, instead of inhaling from the electronic cigarette's mouthpiece.
The "dripping" method produces a stronger hit in the back of the throat when inhaled, and a more pleasurable taste, according to the study referenced in Time.
Although the study doesn't suggest health risks, long or short term, it may be something you want to watch out for with your kids.