When should I introduce English to my son?

I am fully bilingual in Chinese/English. I've focused on teaching him Chinese first. My son was slow to speak. Now that he is 2 and is finally starting to grasp the language, my father-in-law wants me to start teaching him in English. However, I think this will only confuse him as he was such a slow speaker and want to wait until he goes to a predominantly English speaking preschool to learn English (just like I did). However, my FIL thinks that will put my son at a disadvantage as he is a shy child and does not like to say or do anything until he absolutely knows what he is doing.... What do you think?