Good advice from CofE. The Sheraton is overrated, over priced and overcrowded. The Protea is quite expensive (although you won't be paying I guess) but more modern and it's also very slightly closer to the airport. The food is better than the Sheraton too.
It's located on the easier side of the dual carriageway from the terminal and your driver will be able to do a U-turn when he collects you for the return flight as there is a cross carriageway junction just down the road.
Hope this helps.