My three kids grew up in suburbia and rarely bothered to venture into the city. They had active social lives and were more likely to meet up at places like The Fiddler at Rouse Hill with food, live music and plenty going on.
'Eat Street' at Parramatta is another option, it's lined with restaurants, bars and cafes and is at the opposite end of town to Westfield, this precinct has grown massively in recent years. I imagine it's probably much the same in other areas across Sydney.