The powers of a distribution trust director over any discretionary distributions of income or principal, including distributions pursuant to an ascertainable standard or other criteria and appointments pursuant to section 633A.4215, shall be provided in the trust instrument and may be exercised or not exercised, in the best interests of the beneficiaries as a class, in the sole and absolute discretion of the distribution trust director and are binding on any other person and any other interested party, fiduciary, and excluded fiduciary. Unless the terms of the document provide otherwise, the distribution trust director shall direct the trustee with regard to all discretionary distributions to beneficiaries and may direct appointments pursuant to section 633A.4215. The distribution trust director may also provide direction regarding notification of qualified beneficiaries pursuant to section 633A.4213.