Thanks! Another great idea. This whole thing is trial and error this year!
I actually had a discussion with them and tried to make it as generic as possible. Something like this:
We know that some eggs will not hatch out chicks. If we don’t see any chick developing, it might get a weird smell so we will have to throw that one away. That could mean it had harmful bacteria inside that we want to keep away from our healthy eggs. Also, sometimes chicks will get all the way to the end of a hatch, but not be strong enough to hatch out. It will be sad, but not everything in nature turns out the way we wish it would.
One of the kids asked, if her egg didn’t make it, if she could do a little funeral or make something to honor it.

I thought that was super sweet, so I might let the kids who want to make a card or picture for their chick if it doesn’t make it, and we can hang them next to the brooder box so they aren’t forgotten.
Kids are awesome…