[First Presidency Letter]
Must all opening and closing prayers in meetings in which the sacrament is administered be offered by those holding the Priesthood?'
Any member of the Church properly called by the presiding authority in a meeting may appropriately offer either the invocation or the benediction. It is preferable, however, to have the Priesthood officiate in prayer at a regular sacrament meeting. The one who presides holding as he does the Priesthood, is entitled to inspiration as to how the meeting should be conducted, and when he, by virtue of his office, feels impressed to call a boy or girl either to open or close a Sunday School or other auxiliary association, he is not violating any rule of the Church.
[First Presidency, Letter to Joseph F. Merrill, as quoted in Minutes of the Apostles of The Church of Jesus Christ of Latter-day Saints, 1910-1951, Privately Published, Salt Lake City, Utah 2010]