Cape town is not the best place to dive from IMHO. However don't let that put you off.
Things to do, places to stay.
Go to the Aquarium and book to dive in the predator tank. Your entrance fee is included in the price of £40 for 30 odd minutes of great fun. You could check out the predator tank first but that will cost you an additional entrance fee. The rest of the aquarium is also fantastic.
Have an anniversary dinner at Morton's on the Wharf at the V&A centre.
Go to the local market down at the stadium.
Arrange cage diving at Gaansbai (We use white shark ecoventures but they all seem pretty on the ball).
This was where we stayed and the owner Chantel did everything she could to make our stay enjoyable, she was a very helpful and friendly host and the guest house is based 10 minutes walk from the V&A centre (Where the aquarium and just about everything else is based).
Guest House
Also Chantel can arrange other things for you such as the cage diving, aquarium diving etc...
Other things to do.
Go on the wine route and visit the Spiers vineyard. Go up table mountain, go to cape point, go to Robben Island to see the prison where Mandela was kept.
You will have more than enough to keep you busy without worrying about diving and I was more than happy with just a dip in the aquarium and the cage diving (Awesome). Cape town has so much to offer.
If I can provide any more info Noel then give me a call (I think you have my number but I can PM it to you if required). Also if you are interested I have edited the footage from my trip and you are more than welcome to have a look at it.
Is Team Bunny at the dive show on the Sunday?
Best regards to yourself and Dawn,
Daz