Old Airport Express and Airplay

I have a 802.11g airport express I am trying to hook up to a stereo in order to use airplay from my iphone 4 and macbook. I have the AE hooked up to my linksys EA3500 router via an ethernet cable and the light is green on the AE. Also, the the linksys smart wifi recognizes it on the network. However, none of my other devices have the airplay option to stream to the AE. they don't even recognize it. I also have an ATV. This still works fine and all devices can stream to that. Is there a way to make the macbook and iphone recognize the old AE on the g network? Or can I stream to the ATV and then to the AE?

Thanks

Also

I am running OSX10.6.8 and using Airport Utility 5.5.3.