I know that, in order to tell "people" (plural) with no numerals, we must say люди. Человек is used either for singular with no numeral, or for plural with numerals. Consequently, 2/3/4 is followed by человека, whereas from 5 upward it's once again человек, a kind of irregular genitive plural with null ending (like the words волос, сапог, грузин).
Like the word for person/people, the word for "kid" features two different roots, either for no-numeral plural (дети, not counting the expression трое детей) and for singular (ребёнок).
That said, which word should be used when trying to attach a numeral to the idea of "kid"?
2 kids - два ребёнка?
5 kids - пять ребёнок?