The power of attorney for health care shall (1) be in writing, (2) identify the principal, the attorney in fact, and the successor attorney in fact, if any, (3) specifically authorize the attorney in fact to make health care decisions on behalf of the principal in the event the principal is incapable, (4) show the date of its execution, and (5) be witnessed and signed by at least two adults, each of whom witnesses either the signing and dating of the power of attorney for health care by the principal or the principal's acknowledgment of the signature and date, or be signed and acknowledged by the principal before a notary public who shall not be the attorney in fact or successor attorney in fact.