Help me save my daughters

I would normally not ask for help from anyone,  but my back is up against the wall.  I have had joint custody of my girls,  but their mother has done everything in her power to keep them from me for the past 11 years.  In May,  my ex wife's own daughter called me,  and asked if I would be willing to take my two girls into my home.  I immediately agreed,  and two weeks later, they arrived at my home from Texas. We painted the room,  and purchased beds and dressers, and prepared for their arrival.  Things have been going well.  Last week,  I received papers from their mother stating that she is taking me to court to take the girls back.  They have confided to me how incredibly dysfunctional and abusive their lives have been in her care. I contacted a lawyer today, and she feels that i have a great chance of obtaining full custody.  However,  she is requiring a  $2500 retainer to represent us in court. We have a very short time to aquire the funds to hire her. Our court date is set for September 4th. I am in a very tough situation, and I'm praying for help. Please consider my request to help me give my daughters the opportunity for stability and a better future going forward. Thank you for reading my story.