Advice needed

This is a complex problem so please bare with me as I try to explain situation. Son has been married for 2 years. They have a son who is one. Son and daughter in law are both recovering addicts. His wife has been relapsing. She wants to move back to her hometown and live with her elderly parents. Her father is extremely ill. I think that her parents have a right to know that their daughter is relapsing before she moves in with them. What do you all think?

I don't necessarily want them to stay here. I just don't want them moving in with her parents. Her mother is an addict too. Also, my son has found texts that make him question her fidelity. He has agreed to move because he is afraid of losing his family. My son was recently diagnosed with hepc. If they move he will lose his health insurance which he obviously needs to get treatment. They are moving with no job, no money etc. I have reason to believe that she wants to move so that they will be in her state which is more favorable to mothers in the event if a divorce. So worried about the safety of my grandchild!