Airgroup is not needed when all devices are layer 2. Airgroup is used to bridge subnets separated by layer 3.
If your Apple TV's for instance were hardwired to a subnet which we will call VLAN 10 and your wireless users were on VLAN 20 they would not be able to discover each other.
Apple uses the Bonjour protocol for discovery of iOS devices for Airplay and Airprint. Since Bonjour is a broadcast protocol it would not be allowed to propagate across VLANs for obvious reasons.
In order for these devices on different subnets to find each other Aruba built airgroup into the InstantOS. Each AP can act as a bridge for discovery of the iOS devices as long as each AP can "snoop" the other VLAN(s). To make this happen you would need to present each AP with a trunk to your switch which gives them their native VLAN as well as the wired VLAN where the iOS devices are connected to.
Airgroup will then table these devices and allow the wireless clients to discover them. The traffic is then converted from broadcast to unicast and the wired network takes care of routing the traffic to the end device.
In your case everything is on the same layer 2 subnet so Airgroup offers no benefits as far as I know. In fact in your experience it actually disables the service.