I have recently been given temporary custody of my granddaughter by Child Protective Services?

after she went to the school nurse to show bruises she had after her mother grabbed her by the upper arms and throat the night before. My son now wants to file for custody of her, but neither he nor my husband and I have the money for an attorney. CPS is currently investigating the incident and it could take as long as 60 days, so for now she's safe with us. Does anyone know if we have to obtain a lawyer for this, or can we just go before a judge under the cirstances and gain custody?