TheEF-S 18-200mm f/3.5-5.6 IS is a major compromise - a one-lens solution that suffers from distortions at both ends and doesn't offer great optical quality. Optically, theEF-S 17-85 mm f/4-5.6 IS is similar to the 18-200mm - not great (though less distortion). If you have the budget, the newerEF-S 15-85 mm f/3.5-5.6 IS lens (which replaced the 17-85mm) offers much better optical quality (and there's current a Canon USA rebate on that lens). I'd recommend the 15-85mm as an excellent 'everyday/walkaround' lens on a 1.6x crop (with the caveat that at f/5.6 it won't be very good indoors without a flash).


Note that the 75-300mm lens is a cheap lens with worse IQ than either of the lenses you mentioned above. If you can obtain it, the 70-200mm f/4L offers much, much better IQ - if you're buying a new dSLR it will have reasonable resolution, and a cropped 200mm shot from the 70-200mm will end up looking significantly better than an uncropped shot from the 75-300mm. You might consider renting an L-series zoom (from someplace like lensrentals.com) for your trip - either the 70-200 f/4L IS, or the 100-400mm f/4.5-5.6L IS which is a great safari lens.