Outdoor Wedding Music

The cheapest option is connecting a stereo to a computer, and then just have the mic run through the computer (would have to be something compatible with 3.5mm not XLR unless you use adapters, which are easy to get at any music or audio store.)
This summer, I worked at a summer camp, and they just had a regular speaker on a stand, and had mics and a guitar plugged into that. I know Costco sells ones that are compatible with Bluetooth and two mics without needing an external mixer. Long & McQuade does rentals of speakers and mixers with all the cables and mics if you want to go that route. A wedding I was recently at did the rental option and with an 8 input mixer, they were able to have two mics, a computer plugged in, and if anyone needed more, it can also handle instrument plugins like guitars and keyboards. You will need someone to be using that during the ceremony and possibly setting it up again at the reception venue, so that is something to keep in mind. I do sound mixing at a church, so I'm familiar with those kinds of systems, and I'll probably ask someone else who does sound with me to do audio for me.
Basically, if you're doing a combination of live and pre-recorded music or a very large area, rent a mixer, mic and speakers. If all you need is a mic and a way to hook up a phone or computer, buy or rent a speaker that has Bluetooth or 3.5mm and XLR options. Whatever you do, just make sure to test it first with enough time to grab something else from a store if needed.

Speakers provided by the venue would be great if they can do something for you for music. The device you have the music can ben connected to the main unit would be useful so it can be played on all of them.

I do wish now I had an idea of where the DJ was setting up his table for playing the background music that didn't get heard on the video poorly made.

Thanks for all the tips ladies

Defineitly chat with your venue, because if they don't have these items to offer, they may know preferred vendors for their space that can rent/provide those items.

If you're having a dj see if he or she can do your ceremony as well. That's what we did for ours and he brought a speaker for outside during our ceremony

Going off of what Carine said, if your venue does not have a mic to use, I suggest checking out rentals? I know in Edmonton you can rent a giant speaker and mic if you don't want to have a DJ service.

I'm using Spotify and they have a speaker and Mic that the venue provides, see if your Venue recommends anything or they might even have something available.