Bottom line up front: if you're wondering if you should just book individual tours and activities or go with Extreme Scene (Gavin), just go with Gavin -- you will be very glad you did.
We only had three days to spend in Cape Town and, due to an unfortunate travel incident, ended up with only two. And yet we crammed in a full-day Cape tour, shark cage diving, and paragliding. We had been scheduled for a sunset harbor cruise as well but that was cancelled due to weather. And that's part of why I so strongly recommend letting Gavin handle your arrangements -- when things happen (and they do, whether it's weather or travel difficulties or minor problems with tour operators), you will want Gavin to resolve those things for you rather than spending your precious time and energy doing it yourself.
Our Cape tour was excellent. Our guide was Granville, a truly charming and knowledgeable fellow. He not only showed us all there was to see, his commentary ranged beyond the sights to include history, current events, politics, sports, and anything else you wanted to chat about. He was kind to my whole family and a gentleman throughout. As for the tour itself, the big positive distinction here is that it's a private tour so it's exactly what you want it to be -- nothing more, nothing less. If you're not sure, you can just let Granville choose the itinerary (that's what we did) but even then, just tell him what you're interested in and what's not so important to you. As just one example, we asked Granville to find us a halaal restaurant for lunch and he easily did so -- it was delicious.
The shark cage diving was awesome. Getting up super early (4:30 am pickup for us) was not so great, but they have breakfast waiting for you (hot and cold items). The guide is very knowledgeable and you never feel unsafe. We were fortunate enough to see three sharks, one of them a really big boy. The jaunt out on the boat only takes about 20 minutes but be warned the waters are not calm.
Finally, the paragliding was a blast. You don't have to have any experience, it's not physically demanding at all, and it's just plain fun. The views are spectacular and the guys will swoop and dive only as much as you want them to (I wanted a lot!).
But let me re-emphasize how helpful Gavin is. From pre-planning to replanning, to keeping in close touch (e-mail, SMS), all done politely and patiently, you could not ask for a better guy to help you enjoy your trip to this magnificent city.