As Joeseph noted above, 'full of hell' is a very odd way to describe children. What I have seen is the phrase, 'full of piss and vinegar' which can be loosely translated to...having a lot of youthful energy or rowdiness, with the nuance implying the children's behavior is a bit unruly. I have seen 'full of hell and brimfire' to describe a sermon or speech given by a religious zealot/fanatic. Hope that helps

In some traditional Christian beliefs, there is an afterlife. Bad people go to a place called "hell," ruled by an evil spirit called "the Devil" or "Satan," and suffer forever. Good people go to "heaven" and are united with God. "The children were full of hell" is a strong way of saying that the children were mischievous and behaved badly. It is a joking reference to the idea that the children might be in the control of evil spirits. Other similar English idioms include "The children were full of the devil today," "I don't know what's gotten into you," "I can't imagine what possessed you to do such a thing." Young adults getting drunk and behaving badly are said to be "raising hell." "Hell" used to be considered a "bad word," even into the 1950s, and people sometimes said "heck" as a substitute. Even now, to say "the children were full of hell" means they were really bad. An elementary school teacher would never say "my kids were full of hell today;" she would more likely say something like "my kids were very challenging today."

It is indeed a very strange sentence, hell is usually used to describe an enviroment or situation. Such as "it was hell" If it has been written correctly, then Im sure it is slang or wrong English. Either way themeaning would be to show something unpleasant about the children, most likely a metaphor for their behaviour.

Thanks for your answering, I totally agree with your explanation.

Merriam Webster and several other on-line dictionaries have the following entry: - unrestrained fun or sportiveness 'the kids were full of hell' —often used in the phrase 'for the hell of it' especially to suggest action on impulse or without a serious motive 'decided to go for the hell of it' I have not heard the 'full of hell' expression myself, but it may just mean that the kids were playing without restraint. The context should make it clear. 'For the hell of it' certainly has no negative meaning.