If son agrees to sign rights over temporary custody does this cover me to obtain health care for the child and enroll him in day care?

Generally, no. You need to file for guardianship of your grandchild.

It may give you that authority. Is there a mother in this case? She may have rights as well. The law providing for this kind of temporary custody is new, and has not been much tested in appellate courts, so I can't tell you for sure. Consult a family lawyer, and expect to pay him or her for the time to research the statute, the legislative history, and any appeals court opinions which may have been published.

To do it right, you need to go to court and be named the guardian for the child. Then you would have control over visitation and everything else.

Check with your health insurance as to what they need, same with day care. If you have temporary custody through the courts and orders stating that, then you should be able to get coverage. If you just did it yourselves, then the insurer will probably deny coverage. The child has to be your dependent.

What you need to do is get to an attorney and file a petition for temporary custody by extended family. The son and the mother of the child would have to consent, or you would have to file like DCF does, and prove that both parents are unfit. It is best to get the consents. Why do you want to deny visitation to someone, this could land you in jail for contempt.

Basically, no unless there is a court order. Most health insurance plans require that you have "legal custody" in order to cover a person who is not your child. Your son can give you a power of attorney delegating his authority to you and that power of attorney should normally be sufficient for arranging day care, school admission, and medical treatment but it cannot give you authority to allow or deny visitation with the other parent unless there is already a court order authorizing your son to allow/deny visitation. And, that power of attorney would not give you any rights against the other parent. If there is no court order allocating parental rights between the child's parents, it is unlikely that your son has any legal authority for the child and, therefore, nothing he can delegate to you.