This might be a case of "be careful what you wish for". "Keypad" usually means push buttons and maybe a few lines of 7-segmet display. This would be OK for showing that one is listening to a CD or TV and basic control, such as choice of source and volume control, but I don't know how they would navigate through a USB full of music.

Is the pad/phone rejected because it is something to carry around, lack of hard buttons, or is it that computers are "complicated"? Could you use a display keypad?

Do you need to be able to play different sources in each room? Do you need keypads in each room? Could you use a central system and Volume controls in each room? If their focus is TV music channels, it does not seem that they are particularly demanding with respect to audio quality, but it does mean that the keypad should have numeric keys or a few keys that can call up favorite channels.