What exactly is the Toraah telling us here?
Seforno: That Moshe carried out the procedure of each Shelichus exactly according to Hashem's instructions. 1
And why does it add "Kein Asu"?
Seforno: To teach us that they neither added anything nor subtracted anything from Hashem's words.
Why does the Torah see fit to inform us the ages of Moshe and Aharon?
Rashi (in Sotah, 12a): Because it was in the same year that Yisrael left Egypt.
Seforno: To teach us (with reference to the previous Pasuk) that despite their advanced age, they hurried to perform the will of Hashem with alacrity. 1