If, in the opinion of the professional person conducting the evaluation as specified in Section 5585.52, the minor will require additional mental health treatment, a treatment plan shall be written and shall identify the least restrictive placement alternative in which the minor can receive the necessary treatment. The family, legal guardian, or caretaker and the minor shall be consulted and informed as to the basic recommendations for further treatment and placement requirements. Every effort shall be made to obtain the consent of the minor’s parent or legal guardian prior to treatment and placement of the minor. Inability to obtain the consent of the minor’s parent or legal guardian shall not preclude the involuntary treatment of a minor who is determined to be gravely disabled or a danger to himself or herself or others. Involuntary treatment shall only be allowed in accordance with the provisions of the Lanterman-Petris-Short Act (Part 1 (commencing with Section 5000)).