Maybe the Others want children because they taste like chicken...
Or, maybe they are is still experimenting and children are easier to deal with than adults when they've been kidnapped. I seen this movie a long time ago called "The Island". Michael Caine and his son were attacked by pirates and the son kidnapped and brainwashed. I think the pirates lived on an Island and had a type of commune. They wanted to use the son to bring different genes into their group, to much inbreeding. The movie came from a book by Peter Benchley, who also wrote Jaws before Spielberg came along.