Concurrent. We initially tried no sound that lasted about 10 minutes until people started saying, "I love that song why can't we hear the sound?"
With three different feeds its unrealistic to have them playing the audio in the same room, as you have found out. How realistic is it to expect people to tune in with personal devices? If it will only be one or two, it may not be worth the effort to even research this. Unlike the airport, the people in your narthex know each other and will likely find visiting preferable to everyone being zombified into their personal mobile devices.
Or you choose ONE feed to play audibly. Rotate between the feeds each week.
You may not be able to please all the people all the time. You can please all of the people some of the time or some of the people all of the time. But sometimes it's just easier to upset all of the people all of the time.