Hi,
There are plenty of great options, do you know where you're going to be working yet? The commute to work will be a big factor on deciding where to live. The Northern Beaches and Eastern Suburbs are very family friendly, but there are many expensive suburbs. How many bedrooms are you expected to get for 400 - 480pw? The western suburbs are usually cheaper and there are also some great, family friendly spots.
Do you know what type of schooling you would like? Public \ Private?
Happy to recommend area if I understand your requirements a little better.
All the best.