Cape Town may well be wet and Seattle-ish; OTOH it's a good time for Kruger/Sabi etc. as it's the dry season (hence the beasts come to the water) and much of the foliage is down, making visibility better. No bugs to speak of either, so you could probably skip Malaria meds if you go up north.

How are you getting from one place to the other? If driving JNB-Kruger/Sabi, it's a full day's drive and you don't want to arrive after dark. We go to that area in Aug/Sept and have taken to driving from JNB to Graskop the day before the stay at the lodge is to begin, visit the various scenic bits around the Panoramic Route, then dash into Sabi Sands the next morning in time to make the evening game drive. That way you're making the most out of your safari investment, whereas arriving in the late afternoon usually means you miss that drive. Remember too that daylight is not terribly long at that time of year.