Don't break it.
Or if you bring a second body along, keep it stowed somewhere away where you're not lugging it around all the time.
My point is to keep things VERY simple. You can't think only about your photographic needs and ignore the practicalities of this destination. This is NOT some easy package safari to Ngorongoro or to Kruger. This trip is a 3 week jaunt through war zones. The entirety of southern Sudan (not just Darfur) has been having a civil war for around 20 years, and northern Uganda has had its own civil war not to mention being in the path of conflicts in neighboring countries. The infrastructure is miserable and the people are extremely impoverished.
Travelling in these parts of Africa is very difficult in the best of circumstances. Having a large pack full of valuable things is a liability, and it's difficult to take around on the available transportation. If you don't economize, then you're going to be pretty unhappy. So my best suggestion would be to leave out the things you're least likely to use.
As for a telephoto lens, a 70-200/2.8 with or without a 2x teleconverter is probably going to be enough if you're going to see the gorillas. Africa has amazing bird life, and it's for that that you might want a longer lens, but again you have to decide how much bird photography you're really going to do.
On my most recent trip to Africa, which was a 2 month trip (for work) in Senegal, I spent a day in Parc Nacionale des Oiseaux de Djoudj, which is felt by many to be the world's greatest bird sanctuary. I managed very well shooting birds there with a 300D, 70-200 f/4L, and 1.4x TC under bright conditions (and this is having gone to Africa for reasons other than photography, so I intentionally did not bring a comprehensive collection of stuff).