Hi David
I had a similar situation. I had some relatives come on a visit visa. I was able to extend the visa for a fee at the immigration department. Bring their passport along with your ID and go to the typing booths on the premises. The typist will fill out a form for you in Arabic for a fee. 5QR. He will instruct you witch counter to go to. Bring your ATM or credit card as you must pay for the visa fee.