This is a duty assigned specifically to the named person who either acts or resigns (or is otherwise unable to act). They can get help as needed but cannot simply not act and select an alternate to chosen by the grantor.
I am not sure I fully understand your question but if an attorney was paid for their services and is unwilling to release the work product, you may want to contact the grievance committee. You may also want to execute a new Will which may be the quickest and ultimately cheapest route.
Most people wait too long to protect assets then wish they could go back in time. Whether it be to get Medicaid while protecting assets from the lookback period, preserve assets after death via a trust, etc., being proactive is always better than reactive-and much less expensive.
A will is too important to permit known or potential defects. It is inexpensive enough to redraft and also get the other documents at the same time updated or drafted, such as health care proxy, living will, power of attorney, etc. I would not gamble that the will is adequate.
Be careful and be sure that at a minimum you know exactly where your children are and how to contact them and that they can contact you. The grandparents are not the father and will not be bound by any terms that bind the father in a court order.
My firm specializes in grandparental rights-one of our partners is on the advisory committee for the National Association for Grandparent Rights. You may have a very strong case for temporary or even permanent custody. Please contact us.