In Pennsylvania, what is required to gain FULL Power of Attorney over a grandparent by the grandchildren?

In Pennsylvania, what is required to gain FULL Power of Attorney over a grandparent by the grandchildren. The grandparent has Alzheimer's and the grandchildren want to be able to take action for her care as well as any other thing that comes up.

The grandkids' parent (child of the grandmother) is also likely going to be asking for PoA as well WITH the grandchildren.