Is children's an adjective

Answer 1

No, because a child is a noun, since it's a person, and children is just more than one child, so children is a noun not an adjective.

Answer 2

More technically, it is a (plural) possessive noun used as an adjective, to mean of or belonging to children, e.g. children's fantasies, Children's Books.

Answer 3

Yes, "children's" is typically used as an adjective to describe something that belongs to or is related to children.