The relationship between the boy and his father can be seen from different angles. I think the boy likes his father a lot, because he doesn’t see Jim as his stepfather or second father, he just wants his real father, and he looks forward to the camping trip with his father. In line 35 after Jim has been looking at the boy’s torch, the text says: But Jim is not his dad.
When the boy and his father finally are together the boy chatters a lot e.g. in line 60: “Have you brought one too, have you brought a torch?”
I think he is happy and nervous at the same time about being together with his father. He talks and asks a lot of questions, but the father is dismissive and answers shortly e.g. in line 37 when answering his son: “Oh,” says his dad, “good, good”. The father is also inattentive when the boy shows him his torch in line 45: “Great!” cries the man. He isn’t looking at the torch.” But the boy decides that it’s OK, because his father isn’t like Jim, and that’s good. Even though the boy likes his father, I don’t think the father is caring like a father should be. He doesn’t ask how his son has been, he doesn’t seem to have any interest when the boy talks to him and asks questions. In line 148-150 the boy asks his father a question: “Dad, hey, do you think that horse wanted something to eat?”