To tell the truth, bilingualism is basically useless, and children can understand some basics. The price is not low, it is better to listen to English songs for children and watch the original cartoons. How good can a bilingual teacher pronounce English? I can't compliment you. If you believe me, like I said.

I am a senior three this year, and my English is very good. I have never studied bilingualism. When I was a child, I just listened to songs. You can let your children cultivate their language first, and then go to New Oriental or somewhere for a holiday when they are more receptive.