Rex, can I add by how jealous I am!!
Hoping to do the same later this year but nothing booked yet!
The big question is, which national park are you going to? The reason I ask is because you get closer to the animals in some parks than others and that will give you an idea as to what equipment you should take. That being said, I guess you don't want to take the risk and get 'caught short'.
I went on safari in Kenya (i went to Tsavo East and Tsavo West) not too long ago and can advise you on what I did and what I would do differently next time:Photography equipment.
Last time I took one body and a small Sony P&S camera. If I had two bodies then I would definitely have done that and kept a wide lens on one and a big zoom lens on the other.
Depending on what national park you are going to, you really shouldn't need anything more than 400mm (in my opinion). However, there was the one occaision where I would have loved (and could have done with) something like a 600mm (it was a leopard in a tree eating a fresh kill). Like I said, it was only the one time but I could have done with it. If you have one then by all means take one out there but be careful where you are changing your lenses, you will be surrounded by a LOT of dust!
I had my 70-300G lens attached for 95% of my Safari drives and found it to be MORE than adequate. My advice, if you have something of a longer range then take it. Your driver may not want to get too close to a certain animal but at least you are covered if you have more reach, so if you have a 400mm/600mm lens - take it. Next time I am sure I will take something a bit longer, just in case the opportunity arises again.
I also took an 18-55mm lens with me, a Minolta 50mm lens, some spare (and fully charged) batteries, battery charger, spare memory card, rucksack to keep it all in. I then kept my memory in a bullet proof case (not literally, but you get the idea) and had in my sight the whole time afterwards due to fear of them getting damaged/erased.....someone above mentioned taking a laptop/external HDD - not a bad idea really.Clothes
I was told that I would need something fairly warm-ish for early morning and evening game drives because the temperature gets cool. I wouldn't really agree to this as it is still very mild, it's just not as hot as the day. Avoid bright colours though, this has been known to scare animals away. Go with neutral colours - khaki and denim are both fine. You MUST take a hat with you as the sun will be very strong. Also take sunglasses and you MUST take mosquito repellant with you. Pictures storage.
I left mine on the memory card but removed it from the camera and kept it in a safe, dry place. You can take a laptop/external drive with you but it might be a lot to carry with you? I don't know where you are staying but it might be easier to take as little as possible unless you are going to carry everything with you. Depending on how long you are going for and which National Park you are going to, you may travel from lodge to lodge so I wouldn't bank on keeping anything in the room.
I know there is a lot of info there so I hope everything there helps! Let me know where you are going and I can advise you further if you want.