Sounds like he wants one receiver and multiple transmitters tho. RF would be better for range also, and allow setting up on opposite sides of a stage for finals or something.
I have a remote that transmits via RF with sparkfun 434 MHz TX to a RX. I have a 2nd TX also, am gonna build up another remote and see how much they interfere with each other (or, how reliably the transmitter sees both) using Virtual Wire. Stopped at Staples tonight on the way home to get a little 0.2L box to put it in.
His remote transmit device could be as simple as 1 promini (or RBBB to be a little less money), 1 Tx module, 1 momentary button, and a battery.
Arduino is in powerdown sleep mode all the time, button press creates hardware interrupt to wake it up & transmit a character (read from 3 inputs with internal pullups, pull a different pin low on each to make it unique) over the RF.
Can be like jeopardy, ignore anything pressed too early.