Never force your children to learn Chinese.
Learning Chinese is an extra hard job for your children. And if they are forced to learn Chinese language, they must pay extra attention and spend extra time to the course that will undoubtedly distract their attention to their regular school course. So, if you want your children to be outstanding in their class in curriculums, let them concentrate to their school works rather than distract their attention and time.

I have a son who since his primary school days, earned the yearly "President Award". Going through all his high school years and college years, he was outstanding among his schoolmates. Four years ago, he finished all his school courses with the highest academic degree. I had never forced him to learn Chinese since he was a child. I just encouraged him to listen to me and his mother's Chinese speaking. Now, even though he cannot speak Chinese, yet, he understands Chinese, and he also feels to be an honor of being a Chinese descendent!

One of my closest friend's family has the same situation, the parents didn't force their son to learn Chinese, but encouraged him to pay full attention to his school courses. His son now also finished his highest degree as a surgion.

Finally, I have to point out that even parents force their children to learn Chinese, they would forget it as time goes on, but they may have losted a lot of shool time!. It is not worth at all.