Here "in his name" refers to the authority to speak as his representative. AT: "to bless the people as representatives of God forever" (See: [[rc://en/ta/man/translate/figs-metonymy]])
The sons of Aaron were the most important Levite clan, but the sons of Moses were also considered to be Levites. This can be stated in active form. AT: "the people considered Moses' sons to be part of the Levite clan" (See: [[rc://en/ta/man/translate/figs-activepassive]])