ALL THE ANSWERS ARE VERY MUCH ON THE RIGHT TRACK, HOWEVER THIS IS WHAT U SHOULD DO:
A- THE RP OF UR CHILDREN MUST BE VALID (EXP. DATE ON STCKER)AND
B- THEY MUST NOT BE OUTSIDE THE COUNTRY MORE THAN 365 DAYS FROM DATE OF DEPARTURE.
IF THE AOVE ARE VALID, THEN THIS WHAT U SHOULD DO:
1-COMPLETE THE APPLICATION FORM FOR RETURN VISA, (COPY url)
http://www.moi.gov.qa/site/arabic/departments/Airport/resources/images/2...
2- MAKE COPY OF THE CHILDREN PASSPORTS + RP + YOUR ID CARD + WIFE PASSP. + RP
3- SUBMIT TO AIRPORT IMMIGRATION AND PAY FEES (QR. 500.00)EACH PASSPORT.

IF EITHER A OR B ABOVE ARE NOT VALID, U CANT DO MUCH ABOUT IT AND U HAVE TO RE-APPLY FOR RP APPROVAL FROM START.

GOOD LUCK