Is it possible to use multiple IR beacons on different channels to control EV3? One IR beacon has very few buttons and I would like to buy additional beacons and use them simultaneously to be able to control more channels. 

I can't find any information if this setup will work. Can anyone provide references or maybe from the own experience if multiple IR beacons can be used?

I don't want to buy them and then figure out that only one can be used at a time.
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.