For Extension of Visit Visa, you need to get the Medical done of your wife, in order to get the visa extended...

Once your Medical is cleared, Take your wife pp, Debit/Credit Card, go to Main Immigration, Get the Extension form Typed From the typist sitting near the Petrol Pump, then proceed to Booth No 4, Get a Coupon, and Wait for your Number....

1 Month Visit Visa Extension is for 200 QAR....