The beneficiaries of a trust executed after July 1, 1991, which omits any of the powers in Code Section 53-12-232 may, unless the trust expressly prohibits it, by unanimous consent authorize but not require the court to grant to the trustee those powers. With respect to any beneficiary who is not sui juris, such consent may be given by the duly appointed guardian of the property, if any, or if none, by the duly appointed guardian of the person, if any, or if none, by either parent in the case of a minor or a majority in interest of the beneficiaries in the case of an incapacitated adult; provided, however, that such consent on behalf of a person not sui juris shall not be effective when the only person consenting is the person who will serve or who is serving as trustee. The grant of any such powers may only be ordered after due notice of any such proceeding has been given to all persons then having an interest in the trust, and in the absence of any objection having been filed.