+1 for the 5d classic. Great camera, not quite as good in ISO performance as the mk ii, but still miles better than your 450d, and still capaable of taking AMAZING images. That way, you save money for glass and an external hdd (VERY important), and won't have buyers remorse when the mk iii comes out. Plus you'll have the cash to upgrade
For lenses, you seem to be pretty sorted. I'd take the:
Canon 50 1.4
Sigma 70-200 OS
are probably the best choices for you. If it was me, I'd replace the 50 with a nice macro lens and add the 16-35L, as I take a ridiculous amount of wide landscape shots, and love all the interesting flowers and assorted stuff you find overseas.
For an external hdd, you probably want at least 500gb, and it needs to be USB powered. The Acer 640GB portable one is good and cheap.
Lastly, I'd take a couple of large memory cards, and two or three batteries. I'd replace the tripod for the trip with a Kathmandu travel tripod. A ripoff if it's not on sale, it's really lightweight and compact, but it isn't the sturdiest of beasts, and I'm yet to try it with a 5d. A monopod could also be useful; you'd take it more places, but you wouldn't be able to have the really long exposures, which is probably pretty important.
Anyway, that's my two cents (or maybe buck fifty by the time this post is finished). Listen to everyone's opinions, and remember you're buying gear for yourself, not all of us. It needs to be the right weight, focal lengths, blahdy bladhy blah for YOUR style of shooting.
Have a great trip, and belated Merry Christmas