This might work:
https://audre.io
It's a plugin that goes on your master fader (any fader, actually, but if you want to hear the full mix, the master fader) and sends audio out to any iOS device instead of the interface outputs. Works both directions, so it's useful for a number of things. I use it mostly to hear how mixes will translate to personal device speakers and headphones. Love it because I can make mix adjustments practically in real time (maybe 100 ms delay). Makes it super easy to make sure mixes will translate.
I haven't tried it with earbuds connected to the phone via bluetooth, but I don't know why it wouldn't work. Probably a more noticeable delay.