price range? cuisine? occasion?
You could go from cafe scenario, opera bar would be nice and relaxed if food isn't your primary concern. Likewise the bar under customs house, or next door to that is young alfred
(http://www.youngalfred.com.au/) pizza cafe from the originaln alberts on oxford street team.
The overseas passenger terminal on the western side of the Quay is full of swanky places, but avoid Doyles as it's not great; it's not even good. Further around in MCA cafe and then of course, options in the rocks including Sailors' Thai (which gets a surprising number of mentions in here considering David Thompson left years ago) and Lorn Nelson (pub).
Being Circular Quay you're going to pay more for the occasion.