Some good advice in this thread, and congrats on the big trip!
I'll echo the advice given, take two bodies!
I would strongly emphasize the recommendation for something along the lines of the Canon 100-400mm, preferably the new MkII This is the trip of a lifetime, spend the money on THIS lens! (not on a single 28-300mm solution!)
If I had had the new version I might NOT have dragged the 500mm prime along
I did in fact bring the 500mm prime and was happy to have it, but I was going for and getting some shots that most would not be worried about ( Boobies diving off the shore, etc)
The new 100-400mm from an IQ and AF speed standpoint, now (nearly) equals the characteristics of a good prime. (it beats some!) This was not the case with the version 1 when I went , so for me, the playing field has really changed.
If you can get a 7D2 or a 1D4 for the 100-400mm II you will also have the ability to add a 1.4x t-Con if desired.
-your 6D, 17-40mm, (lots of amazing wide angle landscape opportunities as well) and 24-104.
One of those lenses will be on your 6D all the time. The 24-105 most likely on the more wildlife oriented islands, and the 17-40 for the landscapes.
- Maybe add one or both of your primes for times shooting on the boat, or in more relaxed conditions.
- Canon 100-400mm IS MkII
- Consider adding a 1.4X T-Con (older Canon or Kenko will do just fine) *
- A 70D, 7D2 or other good crop body.
- * If you go for the idea of extra reach with a 1.4X, then get a body that will AF @ f/8 (7d2, 5D3, 1D4)
A waterproof submersible point and shoot is a great idea as well, and something i had not considered and regret.
Bring extra batteries and chargers for them, and lots of cards. If you plan right, all your bodies can use the same battery.