Today, most states have very defined laws regarding the rights of grandparents. A notarized document does not mean anything, unless filed with the court and the court issues an order articulating the rights of the other grandparents. Setting out everyone's expectations in a notarized statement is a gooplace to start. However, more is needed.
For the sake of the grandparent relationship with the child, it is worth the expense to have an attorney for this limited issue.