"The children are drawing."
Translation:Los niños están dibujando.
I understand "niños" being expected as applying to an arbitrary group of children. However, I think that "hijos" should also be accepted here, as I saw it as one parent talking to another about their own son(s) and daughter(s), which would also be just "The children" in English.
Hijo seems to imply that the speaker and/or listener is related to the child in some way. This word does not make reference to a child in general, which is what the sentence is discussing.