I am South African, don't live in CT unfortunately but just returned from being there for the last few weeks.
I think a week is not long enough to be honest. There is so much to do, and remember that distance is an issue so getting from one place to another can sometimes take a good few hours. As mentioned, the Garden Route from Port Elizabeth to Cape Town has to be up there on the most scenic routes ever, and so much do within the route. But you need a few days at least to do it I think, stopping over at different spots.
I am not married but when i was I never took off my rings, i go out quite regularly at night, and yes I have been in townships, but its not where I would go at night for a bit of a trip. In Cape Town we walked mostly as where were were based it quite close to a lot of places. You would need a car though if you wanted to visit the Waterfront, Table Mountain, and lets not forget the best bit, some wine farms. Up the West Coast is incredibly beautiful as well, think old style homes all brightly coloured with beach views in small towns. THen there is Hermanus where you can spot the whalesbut only after about June July time.
Feb is mid summer so yes its hot. But also its a good time as it is out of peak season here so cheaper and less busy. Schools are back now so you would be blending in to the normal way of life instead of busy holiday time, which CT can be a bit busy for as its an amazing place to go.
So although maybe this time you have decided against it OP, but i think one day perhaps you should reconsider.
Hope you have a great holiday where to you choose to go.