That's right. If there's one male child, no matter how many daughters are in the group, it's 'hijos', not 'hijas'. ^^
When you are referring to children in general in general then it is 'ninos'. And when you are referring to a particular person's children then it is "hijos".
"The children drink water" would translate as "Los ninos beben agua" because in this sentence you are talking about children in general
"His children drink water" would translate as "Sus hijos beben agua" because in this sentence you are specifically pointing out who's children are doing the activity.
Offspring means descendencia like in - él es su descendencia (he is his offspring).
The voice-over for the spanish in normal-time appears to be pronouncing <<comen>> incorrectly, as com-EN, rather than COM-en, as it correctly does for the slow-back. At least I think it's incorrect. Are there any rules in Spanish that change pronunciation based on word context?