Nice coop.
While the chicks are tiny- they could tumble out of the nest. You could possibly put a barrier up at the front of the nesting box for the first couple of days (would your hen still be able to get out and get feed water? - and then put in a little ramp -- they get agile very fast...
Perhaps a ramp to the box would help the chicks- Do you have a photo that would help? If the box is in a safe area - you could put it on the floor of your coop etc. - Provide some more info - and who knows perhaps someone will read it that did the exact thing.
I have put incubated chicks...