Post trip report:
In case anyone checks back on this discussion, I just returned from my trip.
First, whoooweee. If you can get the chance to do this in your lifetime, please do yourself a service and make this trip. Not just for the photos, but for the visual/sense experience. Wow.
Second, I'm just sorting through all the images I took, the vast majority of which were with my new 100-400, and I'm very, very pleased.
I shoot only RAW. Most of my histograms look quite good, and the pictures themselves look good, and even reasonably sharp, with no processing of any kind.
It will take me a while to work through the approx 1000 images (not bad for a non-photo trip with my wife), but this lens seems to have been the right tool for the job.
Additionally, the multiplying effect of the 30D was most welcome over the 5D I was about to buy for the trip (and still will, eventually, for non-safari photography).