Sounds excellent. I went this time last year but didn't really have time to do any safari. Did lots of diving though! Have you booked any of the diving yet? I stayed at the Great White House in Kleinbaai (just outside Gansbaai). Accomodation was excellent. Self contained cottages with log fires. I also managed a bit of diving in Cape Town itself which was decent.
Probably a bit far away, but if you have time to do the Tiger Shark diving out near Durban I would definitely recommend it. However, I am sure you will still have an amazing time.
I would definitely recommend South Africa. You can fly into Cape Town, flights are around £500 I think. I booked through Trailfinders.
It isn't really Scuba diving, as you stand in the cage wearing a mask and snorkel, then just duck down when the sharks come lured by bait on a line. I asked why they didn't offer diving with a tank so you could just stay down there and look around but they said that the bubbles tended to scare off the sharks. Not quite sure I believed that, but there are so many boats out doing the same thing that any little thing that might deter the Sharks from coming to your boat isn't great.
There are so many things that you can do out in South Africa, that I would recommend you only spend a couple of days seeing the sharks. Cape Town is beautiful, there are lots of great places to see on the Garden Route, and the diving on the East coast near Durban is fantastic.
Is there anything else more specific that you want to know?
Does anyone have any contacts or recommendations for South Africa? I want to do both the Great Whites from Capetown and then the Tiger Sharks (in Durban?). Ideally I want to be away for about 10 days in early August (boo, boring work holiday restrictions!) and want to avoid spending the earth if possible. However, it is my 30th birthday pressie to myself, so I want to make it a worthwhile trip.
The Tiger shark diving IIRC is south of Durban in or near Margate. I don't know the name of the operator though. However if you are in that area at that time of year I would recommend at least a day on either Protea Banks (my favourite) or Aliwal Shoal as it should be ragged tooth shark season. Contact Trevor Krull at African Oddysea for Protea Banks.