For those looking for an alternative solution, I'm currently running Mopidy on a Raspberry Pi connected to a old Logitech iPod speaker dock that also has an aux input, and have a music library on a home NAS (Helios4 from kobol.io).

Mopidy acts as a jukebox, streaming files from the server and locally managing playlists and a queue. It enabled me to reuse my old speakers, put a RasPi to good use, and offers a responsive web UI to manipulate the queue from our phones. It was the best low-requirement open source solution I found.

https://mopidy.com/

What I want to do is plug multiple pi’s into aux speakers, a pi to Bluetooth speakers, and then airplay whatever from my iPhone. All the speakers would play the same thing.

How can I do what you’re doing but with airplay and multiple speakers?

Ah, you're in luck. Shairport-Sync [0] should be exactly what you're looking for.

Anyone know an alternative that works with (non-rooted) Android devices?

[0] https://github.com/mikebrady/shairport-sync