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My opinions are as follows, based on 3 trips to East/South Africa:
1. Tripod. Don't bother. You will be in vehicles and moving around with few opportunities to set up and take static shots. It ends up being just "something else to lug around."
2. Filters on lenses. I say yes. UV/Haze or just a multi-coated clear glass. Dust, Dust, Dust. I always carried a towel to wrap camera in on the seat next to me, just to avoid the dust coating that was unavoidable. Some people throw hissy-fits over this issue. I've used filters on lenses since 1969 when I got my first SLR in Viet Nam and have decided that if I am worried about my lens front elements (dust, volcanic gas etching, sea side salt issues, etc.) my mental state is more relaxed if I use them.
3. Re the dust. DO NOT PLAN ON CHANGING LENSES ON YOUR CAMERAS......except at night at the lodge/camp when you are cleaning things. JUST DON'T. My 24-85 (it's old and not weather sealed) had to go back to Nikon for cleaning after my last trip. My 80-400 didn't. see below.
4. Camera configuration. Not being overly wealthy (a super-telephoto costs as much as a trip to Africa.....guess where I want to spend my money!), my last trip I carried my "old reliable" Nikon D700 (full frame) with a 24-85 zoom for close in/wide angle work (and needed it when we parked, like, right next to rhinos and grazing zebras!) and a D7100 (1.5x crop) with the new 80-400 VR zoom. The latter did probably 85% of all my work and the only time I wanted bigger/longer was occassionally on birds. I have been very happy with the quality of the images I got from it. I did carry a 70-200 and 1.4/1.7 teleconverters, as backup, but never used them. BTW, I had a 12-24 with me, but never used it....and probably wouldn't have even if I had carried a third body. Your idea of a small pocket camera is good.........I haven't done it becuase I carry a stabiliized mini-cam (am upgrading to the Canon HF G20 for this fall's trip) with me as well as the still gear. And, if you are wondering....my opinion of DSLR movies is why I have a seperate HD mini-cam. Better quality, better sound, no "focus search" and no "focus noise" on the soundtrack, better motion stability, more flexibility even with having to handle two different pieces of gear. Personally, I would worry about taking a Tamron lens to africa to bounce around in my vehicle for several weeks, and would pay the extra money to rent a Canon lens.
5. Batteries and charging. Never had a problem. If you check your chargers and such (like your electric razor) you will find that they are all rated for 110/240 volts and 50/60 cycles. You simply need a set of universal adaptors. Please note that I have found i need three different adaptor plugs when traveling from Kenya/Tanzania/Mozambique/South Africa. If you check with your tour providor you should find that you will have electricity always DURING THE DAY at the least, and most places not running on generators will have 24 hour electricity. Take enough batteries to run your camera(s) all day, with a backup set on chargers at your room/tent (some small places may have a designated charging station, so use some kind of tape or permanent marking to identify your batteries and chargers. I have never been anywhere where "battery backup storage" would have been useful.
6. Image backup. I have a baby laptop and a pair of 1 TByte external "passports." I tend to backup every night and, as you propose, carry enough Sd and compact flash cards to last the whole trip without re-use.
7. Cell phone. Your U.S. cell phone won't work in Africa without an expensive SIM card and local service. We have an inexpensive international phone with by-the-minute service that we only use for emergency notification. (mobal.com)
Hope this helps and doesn't confuse, and wish you the best of all trips.