Bilingual Babies often have higher IQ's
My daughter is bilingual being fluent in Mandarin and English. I have seen a lot of Chinese parents who are afraid their child will do poorer in English, if they also speak Chinese. This study shows that learning two languages may increase their IQ.
My view is learning a second language, at any age, exercises additional areas of the brain. As you learn a new skill, or language, new neural pathways are being formed due to the theory of neuroplacity.
For raising a bilingual child, what my wife and I did, was I spoke English to my daughter, while my wife spoke Mandarin Chinese. And my daughter decided to improve her Taiwanese in high school, so she is now fluent in three languages.
Want your child to be clever? Teach them two languages: Study finds bilingual babies often show signs of having a higher IQ - Daily Mail
A series I like for Babies, that is basically a Video Flash Card, is: