Ceremony Music

I'm sure there's a place you could hide your speaker like behind some flowers or under a chair or table. And anyone controlling the music will really only be doing so at the very beginning of the ceremony. I don't think anyone would really notice or care.

For what it's worth, I personally don't think it's weird that you can see a person working the audio, or for any of the audio equipment to be visible.

We are doing the same thing, it just makes more sense when dancing isn't allowed.

Our plan is to have one of our friends push play and stop on a phone during the ceremony. I wouldn't worry about trying to hide your speaker, what else would people expect music comes from?

We are also going to have different playlists to play at different times (specific songs for the ceremony, cocktail hour, dinner, specific songs for our first dance and parent dances, and then the reception one). I'm going to train our friend to switch between them and make sure everything is clearly labelled so she knows which is to be played when.

The main struggles with outside sound come down to projection, barriers (ie wind, other noises), and mics. If you have a small crowd and your weather looks good, your Bluetooth might have enough gusto to get the job done. Best thing would be to check the specs online and make conservative guesses based on your space and the requirements you’ll need.
Something you could also consider is you can rent speakers from Long & McQuade for a day or two. Get someone to keep an eye on your playlist for your ceremony and stick your reception playlist on loop for the rest of the day. It’s not as cheap as a Bluetooth but you’ll get great quality without the DJ contract.