Hi, if you want to use an iPad you need an Apple camera adapter to connect a USB device, which is a little clumsy if you are holding the iPad, but it works well. You could use an Audioquest Dragonfly DAC like this, or maybe a Chord Mojo.
If you want to get rid of the wired connection, you may be better off using a streamer that can just be controlled by the iPad, and wouldn’t need a direct connection to it.