United isn't an issue, it's on the list along with listing instructions. Just allow a few days for EK to issue the Zed ticket and ensure you list properly and have enough time at the airport in case listing doesn't work properly. I had a few issues and United's world class customer service agent (not) in IAD almost didn't let me fly saying she isn't there to help out other airline staff!
Anyway be careful with the loads as others have said, the listing tool will give a smiley face and even then, you can check the seat plan on united.com and also see how many of their staff have listed via their website nearer the time. One of my flights had 7 UAL staff but thankfully we got on.