Sounds cool, careful you don’t drop your iPad overboard!
When there is no connection to your pi with Volumio it will automatically make it’s own wifi network. To check this is on go to settings (settings>network>hotspot settings). Make sure “Enable hotspot” and “Hotspot fallback” are on.
When there is no wifi it’ll create it’s own hotspot and you should see “Volumio” network on your iPad. I believe the default password is volumio.
Then you could use the Volumio app from the App Store or connect via safari to volumio.local
Sounds a cool project. I wanna build one for camping.
I’ve only seen the hotspot availability on a fresh install of the Volumio S/W. It’s use is to get you up and running if you don’t have Ethernet. Once you’ve logged into your own home network then the hotspot becomes redundant. It may be possible to alter the config files on existing installation to re-establish a hotspot but the quickest way is to take a new SD card flashed with the latest rev of the S/W and not log in to your home network. You’ll see a new WiFi source on your phone or tablet for the raspberry pi hotspot and just connect to it