As someone who used to shoot wedding videos professionally, the single best peice of advise I can give you is,...
RUN !!!
Run now, as fast as you can, away from that industry!!!
Now that's out of the way, there's no Pentax body that shoots video that will overheat under normal conditions - I have seen the temperature warning once, and once only, on any of my Pentax bodies, and that was a K-01, standing in in direct sunlight, on a cloudless 40+ degree C day in Melbourne, after it had been recording for long enough to fill half of a 32Gb SD card.
Use two cameras, start one recording 5 or more minutes before the other, so that the recordings overlap, rather then having the 20-ish minute record limit leave you with nothing recording at the same time - put the second camera slightly off to the side on a tripod with a longer lens, it'll give you a nice cut-away in the edit.
With Manual lenses, a K-01, K-5, K-3 etc should get about Four Hours of record time per battery. AF lenses you can halve or quarter that time.
Use and external recorder - I will always recommend the Tascam DR-70D for this purpose. Paired with a Rode NTG-2 in to one channel, and some Rode Go's in to two channels - you can easily hide the Go in the Lapels of a Grooms jacket, or use them with a Lavalier mic and pop the transmitter in a pocket. The Go can also clip to the same podium etc the speeches are made from, or be used to relay the sound from the DJ's mic at the reception, or the priests mic if they use one (many now will)
Put that recorder on the camera that stays on a tripod, not one on a gimbal or hand-held. Use the uninterupted audio recording to sync the video in editing.
Lighting, done right, adds dramatic atmosphere, such as a well controlled spotlight with just enough diffusion to soften it - barn doors to shade everyone else, keep the light on the couple, but on them it MUST be soft.
Light bounced of the walls and filling the room, that's what kills mood and atmosphere.
Co-ordinate with DJ/Band etc for smoke and dry-ice effects during reception for dances.
Quoting Clackers
"That's just for JPGs, right? Don't think either apply for RAW or video."
Colour filters for Jpegs affect Video. Use Muted, you can tweak from there once practiced, and you can pull a couple of stops out of the highlights in Edius or Resolve.
Highlight and Shadow Correction, they do have an effect, you'll notice it most when grading.
Now, all that said. RUN!!!
At best, hire in a subcontractor that specializes in the video production, at worst, do it on a decent Samsung phone, S20 Ultra is a good choice, especially with the recent camera software updates.
If you can, and for HD only, buy a Sony VG-30 or VG-900 and get a Monster Adaptor for your Pentax lenses, they're the Only camcorders with S35 or FF sensor that will have the Bokeh to match your photos, every other Video Production Camera that will do so, is out of the price range of most people - BMD Ursa Mini G2 for example. And being Camcorders they don't have record limits.
Have you started running away yet?