When to move hen and her clutch? Before or after they hatch?

Hi, I have 2 broodies sitting on 6 eggs that are at day 18 now. They are in the nest box and there are two other hens in the larger coop/run, who have been mostly staying out of the way, now, but I have lost 2 eggs that were crushed by another hen. So, while my hens get along very well, I'm worried the presence of chicks may freak them out and they'll hurt them. I have 3 choices: 1) leave everything the way it is; 2) Close off the current nest area with a little wire fence (not ideal in some ways (kind of awkward to set up food/water in that space and it's right next to the main watering spot), but do-able); or 3) move moms and eggs to a dog crate inside the large coop/run. I think I'll move them to number 3 eventually, but I'm wondering if I should do it before the hatch or after. The Storey's Guide says not to move them from Day 16 until after the hatch. I'm also concerned about the broodies breaking from the move or getting upset that they can't leave the closed-off nest, so I'm trying to wait until the last minute to change things.
Any thoughts?
Thanks!