There is a form available for this, fill in the necessary details, attach copies of your Passport, RP & ID and your son's passport, departure date page, RP & ID copy . You may contact immigration office near the airport.

You should have done it before 6 months from the departure date. By paying a sum of QAR 500/- the authorities will extend the stay to another 6 months, i.e, by making the stay outside Qatar for about 1 year. But one thing you should keep in mind is to return back to Qatar at least 1 month before RP expiry.

You may take a chance and try your luck....

With regards,