If I were you I’d get yourself a good phone and use the speakers in that. I’ve tried Bluetooth route, but the sound isn’t better than my Samsung phone and Bluetooth in my experience isn’t reliable outside - too many competing radio signals I think. I either stream using the internet, or if I really need to play my own music and I’m close enough to the house to connect to my WiFi I can use Logitech Media Server. But really, outside, Spotify will do nearly all of the time.
Of course it’s quite a different matter if you want loud party music outside , , ,