In Norman Russell’s The Doctrine of Deification in the Greek Patristic Tradition, he says concerning Daniel 7:13:
"The 'one like a son of man' is an angel, probably Michael, entrusted with the protection of the people of Israel. Only later, in Christian tradition and in the Book of Parables (I Enoch 37-71) does he become a Messianic figure, the Elect of God" (p. 67).
Early Jews (including the New Testament authors and early Church Fathers) were familiar with the books of Enoch (they are even quoted by Judah, whose name is translated 'Jude' in English). Ignoring disputes about the original language of the Enoch texts, I am not familiar enough with literature from second-temple Judaism to know if angels are referred to as "sons of men" elsewhere in this time period. Are they?