I quite like the idea that preschooler Quentin preferred Freddy over his father back in the day. We don't see much of Alan, but I get the vibe that he was a fairly strict/traditional dad who expects his son to be tough, stern and sporty - which Quentin isn't, really (swimming aside).
I feel like Alan would've experienced a major shock when he comes to learn that his son prefers his molester over him because of his parenting, and that's why he mellows out and his relationship with Quentin improves after Freddy's burning.
What are your headcanons regarding the relationships between them?
Oh yusss absolutely I adore the fact that Quentin at one point in his life preferred Freddy over his own father, which is why I also think Freddy in the movie tried to paint what happened to him as he was an innocent man to Quentin since his soft spot for him. I think in Quentin's younger teens years say 13 he's super moody and grumpy like the typical emo teen and I can imagine him getting into a heated argument with his father over Freddy, saying Freddy was there for him unlike Alan. It stings, and Alan doesn't try to take it to heart but he can't help it considering what he knows. Because Freddy would always wait for Quentin while his father was always late picking him up which Alan now regrets intensely for letting that creep around his son. I think Alan tries to make up for this by giving Quentin gifts and attention like Freddy did but all the gifts he buys are stuff he doesn’t want or enjoy.