I'd use Lanseria, as I have many times.
The runway is 30 metres wide, with no shoulders. Looks and feels very narrow.
Generally OK to operate in and out of. Always used Execujet.
For a 2 day trip, I'd probably head into Sandton for a hotel. There is more to do. Montecasino is lovely, but it is a bit remote once you've settled in. There is a nice Sheraton in Sandton, as well as a Radisson BLU and the Sandton Sun. Large shopping mall and Nelson Mandela Square, which is chock full of restaurants - including the legendary Butchers Shop.
Just my 2 cents.