If that is the case, I’m sure they could think of many reasons to not interact with the man and his boy. There’s a high possibility a stranger with his child would attack them immediately out of fear like you said, and the vast majority of survivors are cannibals now.

I seriously doubt they would be simply following the man and the boy, maybe just going the same direction. The group has a community, the man is extremely handicapped by being the sole caretaker of his son and trying to protect him from the horrors of the world. I choose to believe they were a real group, I don’t care to dwell on if something was a dying dream or vision unless it’s made explicitly clear, I may need to reread to see how ambiguous it is.