I agree with all Mark's remarks. Bring in a light or 2 and put marks on the floor to keep the presenters where you want them - they'll still walk in front of the screen anyway.
How about finding out what frequency their mic is and simply tuning yours to that? One transmitter with multiple receivers is fine and we do it all the time. You'll need to do that ahead of time, not the day of the shoot and test, test, test.
Is the AC too noisy because of closed off vents? Make sure they are fully open to allow gentle flow. You may need to ask for the facilities guys for help.
It can become awkward to request these things of your client, but they are hiring a professional to make them look and sound their best. You are not Uncle Joe with a camera. By coordinating with them and showing how their personnel can look and sound their best you are offering a great value and show concern for them. If you can adjust the projector, see if you can change the color temp to 3200 or tape a clean piece of CTO gel in front of the lens to match your lights.
Have fun.
Steve
