""Actually, young children are much more capable of learning languages than older children or adults,""
Yes, because their ear is still developing. The best way to teach children a language is for the home to be bilingual. A friend of my mother's spoke fluent Spanish, and only spoke Spanish to her children. To her husband of course, she spoke English. And her children were raised fluent in both languages.
....what is your point? So children who aren't from bilingual homes just shouldn't learn other languages?
My kids learned Spanish by watching Spanish TV, then talking to some Meixican friends. Worked great.