Update:
We currently have 6 out of the original 9 that were fertilized still developing and in the incubator. When I candled last night, 3 are dark for sure, 1 pretty dark, and two are probably 2 or 3 days growth behind the others. Since it is a homemade incubator the temp is probably not consistent throughout, so that could account for the 2 delayed eggs maybe. I will leave those in until at least Wed. or Thurs. just to be sure. We had opened the 3 eggs we took out; they did develop a little, but stopped early on, between 5 and 8 days.
I am thinking Sunday is the due date. We put them in on day one at 2pm, so it just might be Monday. The kids and I have been discussing all the things that could go wrong between now and then, to make the possible disappointment of no success not as much of a shock. I really hope my daughter has at least 1 hatch successfully. However, if not we will repeat the incubation part of the experiment a couple more times, just in case, since it is my son's actual science project to see if Grocery store eggs can hatch.