Textual: The message is most directly for Alma, even though the sons of Mosiah hear it, and are also affected by it. It is not clear whether or not verse 16 addresses one Alma alone, or Alma and the sons of Mosiah. In English, “thee” and the command form of the verb “go” can both serve for singular and plural; even “thy” serves for both plural and singular. The possibility that the address is to all listeners comes from the very specific address to Alma that begins with “and now.” This “and now” appears to be a conjunction that stands in contrast to the previous clause, not one that is complementary to it. Thus the first clause would have plurals, and the last sentence is exclusively for Alma.
If we read the first part as a plural address, then we have the complication of “thy fathers in the land of Helam, and in the land of Nephi.” The plural “fathers” would make sense for multiple listeners. The problem is that if the group consists only of Alma the Younger and the sons of Mosiah (as implied in verse 10) then we have another problem, as only the Alma the Younger could consider any of Helam or Lehi-Nephi as his “fathers.”
A possible solution to this problem would be that the text is using “fathers” to refer to a generation rather than a lineage. If the “fathers” mean those of their fathers’ generation who were delivered from Helam and Lehi-Nephi, then this passage fits for the multiple listeners as noted by the text.