We had the same concerns about safety and road conditions and drivers as well and we didn't have a lot of time and wanted to see a lot. I also agree with pre booking robben island and book the first tour of the morning so that you can adjust if necessary. We had issues with the outgoing boat and then on our return they brought a boat half the size so if you didnt get on you would have been waiting several more hours. Also although it was summer in capetown early december it was windy and cold on the water. Bring a windbreaker or light jacket. Table mountain can be hit or miss in germs of being open and is less expensive after 6pm which could also mean a beautiful sunset. The botanic gardens are also worth a visit if you like that sort of thing. The concierge can provide you with a driver and vehicle by the hour or the day. The driver was more than that really a guide and very good company since we were together for three days. It gets you used to the city and oriented so you will be more comfortable when you drive yourself. It's a good tradeoff. Don't miss wine country. It's really beautiful and has history and good food.
We really didn't feel more concerned in Capetown than in other big cities but we did exercise smart traveling. Didn't bring nice watches or jewelry . Didn't carry a lot of cash or all our credit cards at once. Used ATM in shopping mall. The Hilton is in an interesting area which we liked but is not the waterfront.
Let us know how things go with you. We are returning to Capetown and on to Namibia in October so I'd benefit from recent experiences. Congratulations on your impending wedding as well.