Welcome to the forums!
You are in for quite a bit of travel!
In my opinion you should drop Cape town, and do Kruger only. Kruger to Cape (which you'll be doing twice!) is something like 1300 kilometers. Which is off the top of my head, I stand to be corrected...
The highways in SA are great, you'll have no trouble driving it. Be prepared for s few tollgates though.
Switching to the bushveld camps is a super idea, you will get a far better experience. Having to go out everyday (back to civilisation) is the last thing you want. Except one of course, having to line up at the gate in the morning, hoping to get in, whilst you know that others are already looking at leopards, birds etc.
There are only two hides that you can book for an overnight, and only for one night. Keep that in mind.
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Arriving currently: The photos from our trip!
Overhere!
Feel free to use any of these additional letters to correct the spelling of words found in the above post: a-e-t-n-d-i-o-s-m-l-u-y-h-c