Who is talking in the poem "Once Upon a Time?" Who is addressed and who are "they" that are referred to in the poem?

The poem
"Once Upon a Time" by Nigeria poet Gabriel Okara is written from the perspective of a
parent addressing his young son. The
title and opening line, "Once upon a time," frame the poem as a kind of bedtime story
or fairy tale, as the father reminisces about a (now lost) time of openness, kindness, and
honesty. The group that the father describes and addresses as "they" is never
explicitly defined, but it's easy to infer that "they" represent all of
adult society. These are the people who have forgotten the
innocence and joy of youth and now "only laugh with their teeth" and have
"ice-block-cold eyes." The portrait of "them" that the speaker paints is of
a society of cold, greedy, and disingenuous people who have lost all of their childhood
wonder.

Interestingly, it is clear from stanza four that the parental speaker
has learned to behave in exactly the same way as these people he groups together as
"they," in order to fit in. But, presumably unlike the rest of adult society, the
speaker longs to return to the bigheartedness of his youth: the same bigheartedness that he sees
in his son.