Thanks for sharing the photo's. Always great seeing what people have done.
I have been looking more into the 70-200 F4, my friend is willing to lend me a 1.4 Tc.
The other lens I am looking at is a sigma 120-400. These two second hand are usually under the £500 which suits my budget.
I am on a budget and deciding what to keep for the long run and what to resale is the tricky questions. My general photography when away is reportage and I always document the journey.
Out of the lens I have been looking at, I think I would use after this safari on other holidays and city breaks, 70-200 L F4 or 70-300 L F4.
I'd have to echo and agree with all the advice that hollis and others have given. I went to Rwanda and Kenya back in March, and it was one of the best trips I've taken during my travels.
For Rwanda, I used the 24-105 with my 60D and that was pretty much perfect on a crop camera. I'd think that the 70-200 would be excellent on a 5D2/full frame. You could pick up the less expensive f/4 since you'll be outdoors and the 5D2 should handle slightly higher ISO without any trouble; plus it'll be easier to carry up with you on the hike to get to them. The gorilla troop we visited were out in the open on the mountainside, and I shot in mostly iso 800-1600 with good results. It was a really cool experience!
Here are my Rwanda Gorilla photos - http://jpeacott.smugmug.com ...Rwanda-Mountain-Gorillas/
I haven't been to the other parks in Kenya, but in Masai Mara I purchased the Sigma 150-500 OS; it worked wonderful for me, and I took ~85% of my shots with it. I actually brought my old XTi as a back-up, and I was glad I did. I kept it as a second body with my wider lenses to capture landscape shots with.
Here are some of my shots from the Mara, mostly with the 150-500:
Regardless of what you buy - enjoy your trip! I can't wait to go back and it was one of the most incredible experiences to be in the wild with the animals in their habitats and no fences to be seen.