In addition to the notice prescribed by § 33-7-9, and to notice by publication in the manner as prescribed by § 33-22-11, the petitioner or his or her attorney shall, at least ten (10) days before the date set for hearing on the petition, send or cause to be sent by mail, postage prepaid, addressed to each person whose name and post office address is by § 33-22-2(3) required to be set forth in the petition, as the names and addresses are set forth therein or as then known to the petitioner, notice of the filing, the nature of the petition, and of the time and place set for hearing on the petition, or in lieu thereof a copy of the newspaper notice published pursuant to the provisions of § 33-22-11; provided, however, that in the case of any person entitled to notice hereunder whose post office address is outside the continental limits of the United States this notice shall be sent at least three (3) weeks before the date set for the hearing; and provided further that the petitioner or his or her attorney shall not be required to send this notice to any person sui juris who shall at, or prior to, the hearing waive notice of its pendency in writing either on the petition or by instrument separately filed. The petitioner or his or her attorney shall at or prior to the hearing file or cause to be filed an affidavit that the notice was given, setting forth the names and post office addresses of the persons to whom the notice was sent and the date of mailing of the notice, together with a copy of the notice.