My question involves name change laws in the State of: Georgia

I have two children with VERY unusual last names that have been teased to the point of them not wanting to go to school, I've contacted the school about it but it keeps happening. (its a horrible name for a girl growing up to have the way the kids keep changing it to profanity and sexual comments) Both my children ages 10 & 8 have asked me to change their last name to mine. I divorced their dad back in Oct 2006 last time he had any contact with them was around 2009 when his newest child was born, he owes $13,661.54 in back child support and only started to pay when CSS threated jail and he only pays just enough to stay out of jail. I have no idea where he lives, what his number is or how to contact him. Can I change their names to help prevent the harassment and bullying at school now and in the future without him consenting to it since I have no way to contact him?