I have been in south africa with the 300 2.8 IS 1 and 2xIII and changed the camera from 50d to 5dII as needed, together with a 70-200 4 IS and some more stuff.
This was a good choice of equipment, because it is still hand-holdable and transportable. I had to wear all this equipment with tripod on my back, and i couldn't imagine to wear more than one big white. Yes sometimes more reach would have been better, and yes with the 2x i couldn't manage to get BiF because AF is to slow.
But transportability is everything, what's the use of a 400 2.8 which gets stolen in the hotel, or what helps the best stuff if you couldn't get to your spot with it? So you must find your compromise and for sure you will know the best compromise when you are back from the trip and know whats opportunities you had.
and one more tip: i would not take a long lens without IS, so often you have no time for the tripod or no possibility for it if you can not leave the car for example. 960mm FF equivalent are very unforgiving even with IS. There the new generation long lenses with the newer IS would be much better than the previous generation.