If DXB-USA isn't looking good and you are having to go via LHR then you could look at the MRU-LHR direct rather than having to go via JNB.
On the subject of Emirates .. I've flown on them at least half a dozen times and bro more than a dozen ( all down the back ) and not had a bad experience. As Flasher says their proceedure is to do the meal first and then drinks so if you know this then just ask for a drink as soon as poss after take off ....