I was suspicious that Ginny's love life got so much face time, relatively speaking, than anyone else's. There's no point bringing up Ginny and Michael (and Dean and Ginny later) unless something was going to happen with it.

As for what he'd see in the Mirror, I think he'd see his immediate and extended family, maybe the boys actually behaving, Lily declaring her intention to join a convent and Ginny agreeing to all nude weekends once the kids are off to Hogwarts. (It's a Wings reference. Once Helen and Joe kicked their siblings out of their house and realized they could do whatever they wanted, they decided to not wear any clothes in the house. Unfortunately, they forgot to close all the curtains in the house.)