Notice of any such petition shall be given in such manner as the court may order to all persons who are or may become interested in the real estate to which the petition relates, and to all persons whose issue, not in being, may become interested therein. If persons interested in said real estate do not consent in writing to a sale thereof, personal notice of the time and place of the hearing on said petition shall be given to all persons known to be interested therein. Said personal notice may be given in any manner provided by law, or by the clerk of courts or the register of probate sending a copy of said petition and order of court thereon by registered mail, return receipt requested, in time to give each party at least 14 days' notice of said hearing. The written statements of said clerk and register, with the return receipt, shall be proof of said service. The court shall in every case appoint a suitable person to appear and act therein as the next friend of all minors, persons not ascertained and persons not in being, who are or may become interested in such real estate. The cost of the appearance and services of such next friend, including the compensation of his counsel, to be determined by the court, shall be paid as the court may order either out of the proceeds of the sale or mortgage or by the petitioner, in which latter case execution therefor may issue in the name of the next friend.