Is it possible to use multiple IR beacons on different channels to control EV3?
Yes, it is possible to use up to 4 beacons at the same time since there are 4 selectable infrared signal channels. 

Also, the 8885 LEGO® Power Functions IR Remote Control is compatible with the EV3 Infrared Sensor if you have one of those already (it only has up down rocker switches and no beacon button, so it is not an exact replacement).

Other LEGO remote controls are not compatible.