I was just speaking from personal experience with my flocks... breeding season and being penned is not always the best combo for Guineas, they are just too high strung. Even if they just get out part of the day, it definitely helps the season go more smoothly.
Private places in the run for the Hens to lay eggs behind is a good idea, but I'd make sure it's nothing that a picked on bird can get trapped/cornered behind, you don't want to find a bloody or dead bird. My Hens like to use the medium sized dog crates bedded with straw (with the door taken off), a recycling bin with hay or straw in it, and also pieces of plywood leaned against the wall (secured so nothing falls on the birds). I also made them a wooden frame out of some scrap lumber that I stapled a bunch of small pine branches to and leaned that up against the wall too.... that ate all the pine needles off of it in about a week, but it was still a favorite shared laying spot most of the season, lol.
Your Hens may start laying in the mornings, but they will progressively lay a little later and later each day until they skip a day (my Hens skip a day every 10-14 days or so). And not all Hens lay at the same time or skip the same day. I keep my breeding flocks in until the Hens lay each day... and some days they do not get much free range time, or none at all, but it definitely saves me the egg hunting hassles. And I don't lose any broody Hens or piles of to predators. During the off season they free range all day tho.
Good luck, hope you get lots of eggs!