Until now I've been thinking of the project as needing to output the 30KHz pin on multiple pins (one pin at a time). It occurs to me that since you will only be using one at a time, you could connect one side of all the emitters to a common pin which you modulate at 30KHz. You would enable or disable each emitter by connecting the other leg to a separate pin which was configured as an input to disable the emitter, or an output to enable it. That simplifies the requirements for the 30KHz pulse generation.