Oh wow, excellent help! Thanks everyone!
We've been looking at all the options for the last couple of weeks (I now know the seat pitch, width and recline for all airlines going to and from oz - www.seatguru.com is great but it probably means you end up splitting hairs over the details)
ILovePudding: Thanks for the tip about the bulk head rows, they are quite tempting but the armrest thing would definitely be an issue.
We never considered going economy in one hit, seemed like way too much of a nightmare but I think you have all convinced us with the one hit, three seats thing now.
I hope we can find a flight that lands in the evening, thanks for the tip Bubbaluv!
Wow GMarksTheSpot, that trip sounded like a major expedition!
Marsha, never thought of the premium economy armrests!
Ninedragons, thanks for the tip but we will be travelling in the northern hemispheres summer holiday season (I'm a teacher) and the plane is likely to be rammed so will go for the three by the window.
Once again thanks everyone for the words of experience!
Oh BTW, when the armrests are up and the seats are reclined does the armrest stick out by your shoulder or is it flush with the seat back?