Here you can find a description how to connect multiple iPads using Wireless MIDI (as an alternative connection instead of Bluetooth).
You will need a Wi-Fi router and all iPads must be connected to that Wi-Fi network. The Wi-Fi router doesn't need to be connected to Internet.
Select in the settings of "SongBook to SongBook connection" the connect mode "MIDI connection (via cable or wireless) on all iPads.
If possible, configure the WLAN router so that at least the server iPad always receives the same IP address so that you only have to enter this address once in the client iPads and do not have to adjust it again and again.
