according to your salary; you are entiteld to apply for a family visa.. it is a limited period, mostly it will be 2 years visa renewalble every year..or a yearly one..
your family left in 2006 so automatically the RPs were cancelle so you have to apply a new one.
you can submit all the required doc. (passport copies, children birth certificates your ID card, your education certificate, salary letter, for of the labour dept. and electricity and water bill) to the labour dept. it takes 4 days maximum to get the reply. once you get it.. apply in immigration with the same papers but not the labour form. it will take around 3 days to get the visas .. send copy of the saem to your famiyl and they can then come to Qatar.. once they are here you can go ahead with the formalities of the RP (medical test, CID and finally the RP stamp).