Usually when there is an issue with the AirPlay there are also latency issues with control. With control, most times it's infrequent and manageable but the music dropping out is the most frustrating of all.
Considering that Airplay has a fixed audio latency of 2 seconds, control latency is pretty much to be expected. If the music is dropping out, fix your networking. No way in hell I would stream critical audio over wifi in any kind of crowd, though.
Yes, the ideal situation would be a music source plugged into the mixer and controlled remotely. I thought I found the solution with an iPad/iPhone app called "Tunes Remote" but wouldn't you know, it's not available for purchase in the US 
That's one of my solutions. Ancient ipod (4?) plugged in on stage. Remote works dandy.
https://itunes.apple.com/us/app/remote/id284417350?mt=8
