I use a cheat sheet with large letters, only one or two words of each verse. By the way, why not using an electronic display, now that they are very cheap, located on the floor, 7 feet appart, activated by a discrete pedal ? Any young technician would be able to build it or adapt an existent device, for less than 100 dollars. Check the device first, very carefully, avoiding the possibility of reading "NEXT STOP GOVERNMENT CENTER" in the middle of the song.
Un abrazo - Andrés