You already have the Statute:
655.77 Deposits by minors. --Deposits made by a minor, or made in the minor's name by other than a court-appointed guardian, may be withdrawn by the minor in the absence of an agreement to the contrary made between the institution and the depositor at the time the account is opened. In case of any such agreement, such moneys, until the minor's disabilities are removed, may be withdrawn by the person or persons designated in such agreement.
This says you can.
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