What a nice problem to have to decide which kit to take on an extended tour of Southern Africa!
I see your predicament though in deciding what equipment to take, especially for such a long trip. I wish I can tell you not to take the 300mm prime lens due to packing considerations, but this being my favourite wildlife lens, especially with the teleconverter option, I almost canít see you travelling without it. Trust me, if you do decide not to take it, there will come the time where you will kick yourself for not having it. I find that a 200mm focal length is just slightly on the short side for African wildlife photography.
So my advice is probably not what you want to hear, but I would suggest taking a wide-medium zoom, the 70-200mm and the 300mm prime and pack less clothing!
Bear in mind that wildlife is most active during dusk & dawn and having an F/2.8 in either the 200mm or 300mm prime will be invaluable in order to cope with the low light conditions.
Remember to take precautions for the ever present dust problems and having the right cleaning equipment. It is also a good idea to rather carry smaller size memory cards instead of a few larger sizes.
Namibia & Botswana wonít disappoint, let me know which areas you are planning to visit and I will try to give advice travel options, accommodation and other considerations.
If youíre planning to pass through the Northern Cape, let me know, we can show you around and maybe even work in a mini photo safari.
I hope this helps Ė feel free to make contact should you have any further questions. You can mail me directly at firstname.lastname@example.org
Enjoy your trip!
Kevin a.k.a Kalahari