Rats, I had a whole post full of tips and then I accidentally knocked the cursor focus out of the text window, hit backspace, and Internet Explorer lost the whole thing. Grrrr. Here we go again...
OK, so I'm not a pro either, I do this stuff for fun. That said, I've been asked to help out with video for a few weddings. First thing is to sit down with the couple and hammer out exact expectations. Hopefully your friend is aware that you are not a pro (and thus are not charging the price of a pro) and their expectations will be tempered thusly. This is the part that makes me uncomfortable about doing free/cheap wedding shoots for friends -- I feel like if I goof up, it will be on my head forever. If you feel any way uncomfortable or unsure, say so up front. Hopefully, as has been the case for me, the couple is understanding.
Definitely check out the venue in advance so you know exactly how you will apply any advice you are given. Also ask the couple if they have any specific requests. One wedding I was asked to set the camera on a tripod sitting at stage right, with me standing behind it to move it around. I felt ridiculous standing there in full view of the audience only a few feet away from the groomsmen. But hey, they wanted it. Got a good shot of the couple coming down the aisle at least!
If you get a chance, try to talk to the photographer(s) so they know where you are recording from and where you might be moving. Nothing more annoying than setting up your camera only to discover the photographer plans to stand right in front of you.
I second the idea of a locked down camera somewhere near the back of the room (a balcony maybe?) to get a good wide-angle shot covering the entire wedding party and maybe the first few rows of the audience. You can keep cutting back to this shot and use it as a backup audio track, an audience ambience track (applause, hymn singing, etc.), as well as a reference point to sync up any other cameras or recorders that you pull audio from.
If the venue is providing mics for the minister, any speeches, etc., see if you can talk to their sound guy and ask about getting an audio feed straight from their board. It doesn't have to literally be a cable from their mixer to your camera or recorder. A lot of churches are set up to record their sermons and post the audio online. Maybe they can give you a recording on a USB drive after the service. Otherwise, set up your Zoom recorder somewhere nearby the minister and bride and groom. You can sync the recorded audio from it to your video track later, using your locked-down shot as a reference.
The bouquet-cam sounds cute, but don't overuse it. Sounds like something that could be fun in a 3-minute "wedding day highlights" music video though.
I think the bottom line is to prepare yourself in advance, have your plan all set up and bring everything you need, but be flexible and plan for a few contingencies (what if the spot you chose isn't available? what if the photographer insists on standing in front of your camera? what if one of the guests does? where else can you set up? do you have extra memory cards? batteries? extension cords? duct tape?) Weddings are stressful days and anything you can do to minimize that will help both you and others around you. Have fun! Best of luck to you and to the happy couple.