The good folks at Cafe Tropicana
, while having the best internet connection in Vava'u, understand how slow an internet connection can be when someone is simply trying to do "normal internet stuff" let alone try to down the Navigatrix ISO.
So while you are having a great cuppa and reading your email...or just reading your email, Lisa Molloy, the owner/operator will create a LiveCD of the Navigatrix distribution on your own 4GB, or greater, USB stick...or sell you one for a reasonable Tongan price.
This installation includes the entire collection of charts from the Government of New Zealand available on the internet but georeferenced for use with OpenCPN. On your way further west or New Zealand for the season you're ready to roll.