Lily may know Nott's children, but I'd have to double check on that, but I'm sure they know each other. Maybe she's shadowed him once or twice.
Ginny definitely knows and adores Oliver. He would have played against her during what I call the 'ruthless' part of her career (taking angst of the Pair Bonding thing out on the pitch), so there's that too. Hell, maybe she accidentally caused his injury and felt super guilty about it- leading to friendship? And he coaches her second-born, as well. Potential there.
Aiden! I can see Lily dating him for a while, definitely. And Ginny would be happy to know him professionally.