If you have unlimited leave for sure book a B&B. If you want to max your time, then move on. Another factor is that your flight is from Oz, so your sleep patterns will be in a bit of turmoil...I can't see that you will go to bed before 2h00 the next morning in any case :)
Yes, there is most definitely a safety issue re driving at night - it is not recommended if you try do it yourself. Using a driver puts a different spin on it though. It really sounds here like when the sun sets the gremlins & gruffalo's all come out...
Missed answering the stop light q... Not stopping at stoplights is actually illegal, but generally accepted late night when the drivers are women. If your driver takes the right road - airport, N1 eastern bypass, N4, R556 - then the only stop lights you will see will be at the 2 toll booths.
Then, once on the R556, there are 4 stop streets between the N4 and Sun City, all that gets treated at night by 99% of the locals as yield signs.
Lastly, there is another small factor you might consider, and that is rain ....South Africans in general just can't drive in it. This is where picking the right company to drive with is relatively important.