Hi OP. I’m quite late to this thread, but just in case you are still deliberating...
I lived in Joburg for 3 years 2008-2011, so a bit out of date now. I enjoyed it a lot. Both living in Joburg and travel in the region. I didn’t have kids back then, but lots of my friends did. They enjoyed a lot of sports, outdoor activities and all seemed to have good social lives.
It sounds a bit wanky, but if you can afford an ‘expat style’ life, it helps a lot. We lived in Fourways. Basically compound city. Our estate was huge with a golf course, club house, tennis courts, pools etc. There was a well regarded (by my parent friends) school right at the gate of the estate. Kind of between three big estates. It’s called Dainfern College. There was a Crawford school nearish too as well as the American International School.
Lots of people had their kids in South African private schools. They seemed more academically rigorous and even sportier than the international schools. I don’t think it will be hard to find good schools.
There are loads of malls around with safe shopping and dining. Also lots of gyms. We also lived near some nature areas and a dog park and we didn’t feel too constrained. I had friends in smaller compounds in other parts of the city and they were nice too. I would have been nervous about a stand-alone house, but I know people who live in them and are happy to do so.
Biggest (non crime) problem is traffic so I would try to triangulate work, school, home carefully.
Your OH might struggle to find work though. There were quite strict rules about employment when I was there. I would look into remote opportunities if possible or further study/volunteer work if that’s financially viable for your family.