Don't forget to obtain overflight/landing approvals from the various countries before you set off.
I recall that the payment for fuel in Christmas has to be in cash and AUD but that was some time ago so it may have changed but worth checking.
I would be inclined to use Monterey and Hilo for the first leg as it shaves about 30 min flight time off the first sector which you will appreciate on the day. There is a hotel at MRY adjacent to the tarmac which enables an easy departure. Like Kona, Hilo also has an ILS but the hotels are a little closer.
Enjoy the experience and please tell us how it went.