I'm so sorry that you are going through this! Thank you for protecting her son while your daughter works to find her way back to sobriety. I'm not sure of the answer to your question, although I would say that at least for now, it is not something that needs to immediately be decided. I'm glad he is safe and your daughter can now focus on doing what she needs to do.
I wanted to let you know that I moved your thread to Friends and Family of Alcoholics since that appears to be where you have shared your story previously.
Your daughter knows how to stay sober - I hope that she will dust off those tools and rebuild a life that in time she can share again with her son.