Douglas Stringer has suggested (personal communication, 2 November 2003) that the plural fathers in this passage could be an error for the singular father—that is, Mormon here is referring to Alma and his father, also named Alma. There is one manuscript example where Oliver Cowdery wrote fathers instead of the correct father, in this case as he copied the text from 𝓞 into 𝓟:
In that case, the text is referring to Lehi’s dream, so the singular father is definitely correct. Here in Alma 50:38, the plural fathers is extant in 𝓞. Moreover, the plural form definitely works since Lehi, Nephi, and all the other Nephite fathers highly valued the records and the other sacred objects (see, for instance, Alma’s discussion with his son Helaman in Alma 37). The critical text will maintain the plural fathers here in Alma 50:38.
At the end of this verse, the editors for the 1920 LDS edition placed a comma between his son and Helaman. The comma is definitely intended since it is marked in red in the 1920 committee copy. This comma adds a nonrestrictive meaning to the last sentence, as if Alma had only one son, Helaman. But we know he had two other sons, Shiblon and Corianton, so the comma should be removed from the standard text to indicate the correct restrictive relationship.
Summary: Maintain the plural fathers in Alma 50:38, the reading of the original manuscript; in addition, the nonrestrictive comma between his son and Helaman at the end of this verse should be removed from the LDS text (since Alma had two other sons).