That litany of childhood death sets us up to respond to the developing nightmare on the island of Almonzara in a certain way that enhances the horror of it. Without the historical set-up, we might spend most of our time wondering how, not to mention why, the children of the island are systematically massacring the adults. Given a world-historical context, our speculation roams more widely than it might otherwise. We can begin to imagine the children's murderous "playing" as some sort of divine retribution.
Serrador tells us that he dispensed with an idea developed in the source novel by Juan Jose Plans, which was actually written concurrently with the screenplay. Plans wanted to explain the rampage with some sort of toxic event hitting the island, but Serrador keeps things more mysterious by not explaining it. All we know is that the killing impulse is transmitted telepathically from child to child, and in one case from child to fetus. Explain that how you like. It clearly put the American distributors in mind of Village and Children of the Damned, since they retitled Serrador's movie Island of the Damned for its stateside release. The general vibe of the film is like a cross between the Damned movies and Night of the Living Dead, though the island kids are more happy and playful than either analogy might imply.
The menacingly quiet scene above throws the benign scene below, from earlier in the film, into a more menacing light.
"Who can kill a child?" I'm sure some brave grindhouse types must have said, "Give me a gun, I'll show you who can kill a @$%#!! child!" back in the day.