I would like to quote the last paragraph of this article :
"Knowing two or more languages truly gives kids so many advantages in life. Bilingual kids have the advantage of knowing two cultures, of being able to communicate with a wider variety of people, and of possible economic advantages in their future. Research has even shown advantages in thinking skills among bilingual individuals. But deciding to raise bilingual kids is a decision that should be carefully considered as it affect children for the rest of their lives. Parents need to consider the child's self identity, self-esteem, schooling options, as well as social factors when planning for bilingualism. Becoming bilingual is a special gift parents can offer their children, but the gift must be planned and presented with care for it to be well used and appreciated."