Take 'em all, you know you'll miss something if you leave it out. But keep it hidden and with watertight insurance.
Hermanus is a nice place; there were lots of Southern Right Whales with young there when we went. Good chips in the restaurant I seem to recall.
Be careful, it's the only country where I've been robbed on the street - Cape Town of all places. You might want a peg for your nose on safari, the only thing worse than the attitude of the wild life is its reek
If you are hiring a car don't stop for anyone on the road and make sure you keep the windows closed at traffic lights (not many of those out of the bigger towns).
Safari means early starts and it can be well nippy. Also when we went HUGE spiders all over the place. You can sometimes get reasonably close to the beasties, but you might need fast shutter speeds to get anything decent. I would not recommend getting out of the truck to take pictures.
Have a great time, lots to see and do, fab food.