Lots of great advice on here already, so i will just add a small tip - book your Table Mountain ticket online - not only for the discount and saving time on the line to the ticket window - but to give you increased flexibility. The lift is closed anytime there is too strong wind or clouds over the mountain - which is quite a lot. So monitor the weather and change your plans if need be to take advantage of a calm day - you might miss one of the best views otherwise. And as a bonus, go around sunset - it's amazing.
Definitely take a tour - we got lucky with a 30 year veteran Paul, who knew the park in and out and provided for some unforgettable views.