Ideally, you should have a local scanning server to scan your devices. MAC addresses of devices in remote sites often cannot be retrieved by a remote Lansweeper installation. This is the case when SNMP is not active on the devices.
We have not done any testing with Playbooks, but iPads have no open ports for discovery. The only thing that can be discovered is the MAC address of the network and the vendor (Apple). They will therefore always be listed as "unknown". You can use the vendor info to identify the devices and manually change their device type.