It'll be easier catching up now than trying to do it when he's an adult. Take the long view. How hard is it now versus two years from now? Get him a tutor who is familiar with smaller children and get him started. If he's got the aptitude, he's pick it up fast (especially if he is already used to hearing multiple languages in the home (I assume you use English and Punjabi in the family as well?
Remember, the younger they are the more flexible and receptive their brains will be. My children had no mandarin speakers at home at all but we did use a tutor for the first 3 years for my daughter (he was a PRC from Shanghai) He used their methods of teaching and when my daughter started P1 at CHIJ her Mandarin was better than all of her classmates (and her being the only non-Chinese in the class). Course it helps if your child WANTS to take Mandarin.
I used the power of subliminal suggest on both of my children (cheating in a way

). I started talking to my kids when they were 3 months old the way I would talk to a full grown person. (I've always refused to let relatives, or strangers for that matter, talk to my kids in baby talk from the day they were born (a couple got offended by who cares). Babies learn by imitation, if you talk in baby talk they learn to talk baby talk! (my girl started talking in
sentences at 7.5 months, my son at 8 months) Anyway, from 3 months, I always talked to them about taking Chinese as their second language. By the time they reached kindergarten, they thought "they" WANTED to take the language. So half the battle was already won before they even got on the playing field!
