Guardians may be authorized to invest any money in their hands, not needed for the payment of debts, or for the support or education of their wards, in notes secured by mortgage upon unencumbered, improved real estate situated in this state, or in the bonds or other indebtedness of the United States, or of this state, or in the bonds or notes of any city or town in this state, or in the stock of any domestic building and loan association or federal savings and loan association doing business in this state approved by the probate court, or to make deposits of money in any savings bank or trust company in this state approved by the probate court, as he or she shall deem best for the interest of his or her ward; and may also, under the direction of the probate court, invest any money in real estate or bank stocks in this state or in other safe income producing securities as the probate court may approve; and if a guardian has so deposited any money in any savings bank or trust company or invested the money in stock of any association and deposited with the clerk of the probate court the savings bankbook, share certificate or other evidence of the deposit or investment, to be held subject to the order of the court, the probate court in its discretion may relieve the guardian of the requirement of surety on his or her bond.