This is an introduction, not part of the text. It is not meant to teach a particular type of doctrine, but it is in that very unintention that we may learn something of the nature of the faith that Mormon has.
First, he very clearly makes a distinction between God the Father and the Holy Child, Jesus. This attribution of Fatherhood to someone other than the Atoning Messiah represents a difference in the nature of Nephite understanding of God (see the comments following 1 Nephi 11:18). For Mormon, however, there is no indication of any association between the Father and the Messiah. The appearance of the Messiah to the Nephites resolved that theological understanding. Mormon is not preaching the separation of the two, he is simply expressing it as though it is clearly understood, and certainly it was.
Second, although pre-Messianic-visit theology emphasized the coming Messiah, this benediction assumes the Messiah. The emphasis is not on the not-yet-achieved atonement, but rather on the effect of the achieved atonement. Mormon cites the “infinite goodness and grace” of Christ. This is a reference to the accomplished atonement. None of the theology of the effect of the atonement is referenced however. There is nothing of the indication that there are two deaths from which man needs to be saved (2 Nephi 9:12; Alma 12:16; Alma 42:7-9; Helaman 14:16). The emphasis in Mormon’s statement is on faith. Faith is a stronger scriptural theme after the atonement than before the atonement, even though faith was a principle understood and taught among the Nephites.
Mormon’s introduction reflects a theology that is post-Messianic-visit, in a context where he is not explaining those doctrines, but simply assuming them. Obviously they form the basis of Mormon’s beliefs. Just as clearly, they also form the basis of Moroni’s beliefs, for Mormon is simply able to assume that his son will read this as an introduction, and not require any explanation.