Section 5. A testamentary guardian and a trustee under a will shall be exempt from giving sureties on his bond, if the testator has ordered or requested such exemption, or that no bond be required, or in case of a trustee, if all the persons beneficially interested in the trust, of full age and legal capacity, other than creditors, request such exemption; but not until the guardian or conservator of any person under disability interested therein and such other persons as the court orders have been notified and had opportunity to show cause against the same. The probate court may, however, at any time require such guardian or trustee, or a trustee appointed by the probate court, to give a bond with sureties. The court may, with or without notice, exempt a trustee under a will holding property for public charitable purposes from giving surety on his bond.