I suscribed to a thread in the hatching section. It went for a long time, people would submit their setting number of eggs, and their hatching percentages. The idea was to add your numbers to the previous posters. The idea was mathematically sound, as any one person can have a great hatch or a terrible hatch, but over time with a great number of eggs counted, it becomes more statistically stable.
And what eventually emerged, was that it didn't matter whether you were hatching with an incubator or a hen, the overall average was about 50%. So if you are above that you are doing well, if not, it did not go so well, but obviously it often does not.
There are so many variables, I just had a hen only hatch 3 out of 13, ugh!
Anyway, I think centuries of keeping chickens have lead to this old advice, "Don't count your chickens until they have hatched!"
Better luck next time, and as for doing it for the grandchildren, that is a great idea, mine love to see them.
Mrs K