That's a good offer. Normally, in first 3 months you are still in probationary period and in process of your Residence Permit and Qatar ID. After completing these three things then only you can start processing your family visa and these requires 1-2 months. After three months you most probably settled yourself in Qatar and adapted with the lifestyle here... In that case, it would be beneficial for you and your family in your transition stage... Goodluck!!!