My son was very happy at TutorTime in Tai Tam, which wouldn't be too far for you from Chai Wan. It is bilingual (English/Mandarin), but Chinese knowledge isn't expected. My son attended TT's playgroup starting at around 1 1/2 years old (when we moved to HK) and completed the K1 (3 year old) class before enrolling in his current international school.
TT in Tai Tam offers classes through K3 (6 years old), which would give you plenty of time to apply for and enroll him in a primary school for the next stage of his schooling.