Well as vegas said if you have enough income.. Plus your sponsor i mean the company which is sponsoring you for a job here in Qatar you have to tell them that you are a single mum and wants my children here so they will give you a NO OBEJCTION letter and with the help of that letter you can apply for a visa for your children.. i guess that's how it works.. but first you have to come alone to qatar i mean when you will come first time to Qatar than..... i guess i told you the right things..hope it will be useful to you

Thanks :)