If a designated caregiver agreement entered under chapter 257A before April 15, 2000, would have become operative but for the operation of Laws 2000, chapter 404, sections 1 to 13, the parent who executed the agreement, or if the parent is unable to act, the designated caregiver under the agreement may file a petition under section 257B.05 to request that the designated caregiver agreement be approved by the court as a standby custodian.