More than anyone, your daughter needs help. A suicide attempt is often a cry for help. You must talk to her about getting counseling, not about leaving her husband. Tell her she needs to be stable to be a good mom. If she refuses to speak with you, go back to social service and insist on seeing another case worker.
Somebody has to be covering for the case worker on leave.
If all else fails, contact a lawyer and your state s grandparent s rights organization. Usually I advice staying out of a married child s affairs. But, in this case, you have reason to worry. Your daughter desperately needs help as does your grandson. There is no law that says you must be allowed to see them.