Hey there!
With regards to Cape Town, such a good idea to go a few days ahead of time- there is just so much to do there, both in the city, and the greater surrounding areas.
Depending on your interests, you could go to wineries, safari parks outside of the city, go up table mountain, or head to Simons Town south of the city to see the penguins there.
Down by the waterfront, the V and A Waterfront is really well done, and you can also take the ferries out to Robben Island from there.
For historically significant areas within the city, I'd recommend the District Six Museum and Bo Kaap.
Check out this video for more information:
https://youtu.be/ISuHOkgNGVs
Enjoy Cape Town!
Jeremy