Mid December road trip to Sydney or Whitsundays

Hi All,

I am planning a road trip with the family (wife and 3 kids under 8) to either Whitsundays or Sydney (Wollongong area) between 15-21 December.

Sydney to visit family and close friends, Whitsundays to explore and see new things.

How would the weather be heading up to Whitsundays that time of year? We will also be camping all the way there (Whitsundays) or Sydney.