I’ve shot years of wedding solo and your friends ask is a tough one as shooting is only a quarter of the challenge. That aside. I just did my first video with the x-t3 and focus was a challenge and the stupid stopped recording in 4K. At least it counts down on the screen to give you a heads up on when it will quit recording (so you can try to get critical vows and such...or an external recorder talked below)
ok, the overheating issue. An external recorder is the way to go. It should give you 4:2:2 10 bit 4K and no limit on recording time (completely test this as I have xt3 not xt30 experience) the external recorder needs to have a monitor as part of its package. (My past experience w/ a Canon 5D mark III) it was the back LCD that caused the heating issue so switch to the eye viewer and test to confirm it won’t overheat anymore.
on other stuff. Work on video focusing a ton and review footage on a large monitor. HD isn’t forgiving and 4K is even less forgiving. Use one lens and get as familiar as possible using it with video. Dreaming of what’s possible (different lenses, etc) vs the reality of only have one chance at getting it right will put a lot of stress on you. Switching gear in the middle of all this will add stress. (Where do you store the other gear, What pocket is it in, how/when to switch back, where’s that lens cap, did switching introduce dust, a hair, finger print or a little fuzzy thing that will be on all your footage now)
Sound: shotgun mic like Rodes with fake fur (deadcat) windscreen on camera as it will isolate most unwanted camera and all your breathing noise (you’ll be huffing/puffing at sometime). Small recorder with small lavalier mic for groom. Recorder goes in jacket breast pocket. Turn on at least 10min. before ceremony and put tape over on/off switch (if groom goes to bathroom ya don’t want him messing with recorder because he’s under stress too and may/will forget to turn it back on)
hope I didn’t overstep your ask too much.
just want to help you and your family.
good luck!