Originally Posted by GibSpmuh

The airport is easy to get to from the city, before 7am there's not a whole lot of traffic to worry about and you'll be going in the opposite direction to most of it as well. The Marriott Sydney Harbour is also located close to the Circular Quay train station, so it's easy to catch the train too, though with two adults and a child the cost would be about the same as a taxi anyway. It's only a 15-20 minute journey with either option though, so pretty quick.