Thanks, everyone... this is all really helpful. It seems like there are quite a lot of different options potentially, so I'm struggling to figure out which would suit us best.

Please forgive me for asking one or two naiive questions:

1. I assume I'd be best advised to use the same airline (or airline alliance?) for the entire journey...? Presumably then if one flight didn't arrive in time for the next, I would have some assurance of being put on the next flight??

2. If stopping overnight somewhere, do you think it would be better to have a couple of nights in that location to make hte journey a bit more of an adventure, rather than a drag of constant travel? My wife and children haven't been to New York before, so it'd be nice to show them some of the city if it fitted in with our plans. In fact, none of us have seen much of the US at all, really... but maybe we'd just be best pushing on with the journey, getting to Hawaii, and relaxing...

I should have said that I'm probably looking at some time in the last two weeks of October. I don't know the precise dates yet, but it needs to co-incide with the October half term vacation we have here in the UK (which maybe will be a more expensive time??) I *think* we'll be able to leave any time on or after 18th October, and will need to be back by 3rd November at the latest (but each of those dates could be a week earlier, I'm just not 100% sure yet).

Orbitz, Travelnow, Expedia, Sidestep, Mobissimo... they all seem to allow me to search for the first 2 weeks in October, but not the last two... no luck with Kayak or Farecast either... I guess this will change in a fortnight??