There was a link buried in the cruise summary I posted earlier: http://www.naia.com.fj/tonga/index.html

It still seems to work, and it should definitely provide the best info about the cruise.

Our time on land in Tonga was limited to the layover between flights on ANZ. On the way out we simply tried to get some sleep at the hotel after arriving around 2AM. Unfortunately construction commenced promptly at 7AM outside my window. On the way back, we squeezed in a quick island tour but did not have time for much else.