iPad or iPhone can't see Airport Express but Mac can.
Both iOS devices are on v8.1.3.
My Mac can see the Airport Express and send music to it.
iMac (27-inch Mid 2010), OS X Yosemite (10.10.2)
User profile for user:
CarlAVII
User level:
Community Specialist
,
The article linked below details a number of troubleshooting steps that can help get AirPlay to work correctly from your iOS devices.
Resolve issues with AirPlay and AirPlay Mirroring from iPhone, iPad, and iPod touch
http://support.apple.com/en-us/TS4215
All my best,
Allen