There is also a shuttle from the coach parking (downstairs from the City Lodge) that will take you to the Emperor's Palace Casino complex - IIRC the shuttles run every 20 minutes and only take 5-10 minutes. Here you will have a selection of restaurants.
Without needing a shuttle as Johan Rebel has said, Quills at the Intercontinental Hotel is about the best you will get.
You also say that you have a long layover on the final stay, you could also consider jumping on the Guatrain from the airport and being in Sandton in 15 minutes, where you will have a wide variety of shops, restaurants, bars etc.
Credit cards will be accepted pretty much everywhere, but doubt any (except very touristy places) will accept US$ cash, and if they do, I would expect a very poor rate of exchange.