In Tanzania there are a lot of wide-open spaces and most reserves forbid vehicles to go off-road. This means you can be a long way from the animals. For that reason I would strongly recommend getting the 1.4x TC - it barely has any effect on IQ or AF.
A lot of the time the animals are stationary, or moving slowly, so AF speed doesn't really matter. However, the more interesting shots tend to be when the animals are moving - sometimes very fast. For those shots you want a camera/lens combination that can keep track of a hunting Cheetah - that means the 300 + 1.4x goes on the 7D.
For a 2nd setup, whilst out on safari, I prefer a 70-200 f4 IS. I go for the f4 rather than the f2.8 mainly because of weight (although cost was a big influence). I'll also have a 10-22 in the bag, just in case.
