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

I would like to change the surname of 2 of my children to my surname, when I have looked around on how to do this it says that I need permission from the father.

He has signed away his rights as a father as he abused one of them and spent three years in jail and was then deported.

Do I still need to get his permission to do this?

Also what is the usual cost of this, a friend told me it would be about $350 per child.

Thanks.