Hey TiaRC, thanks for the quick response. I will leave the "family" intact and watch for trouble. Now how long after hatching does the hen leave the nest? There are eggs of progressive ages in all three nest boxes so potentially there could be hatches every day for the next 20 days.
My hens most often leave the nest starting the second day, though they may stay longer if they have food and water within reach for the little ones. Staggered hatching often results in the loss of either the late eggs or the early chicks, so your plan to remove unhatched eggs to an incubator is a sound one. To increase space under the broodies you could also candle the eggs on about day 10 to 12 or so of when you think they began setting and remove the ones which are obviously far behind in development at that time to the incubator. That isn't a big deal unless the nests are very crowded with eggs, because overcrowded nests can also cause problems (hen can have difficulty shuffling them to maintain temps over all of the eggs.
If any hatch in the incubator within a few days of when the hens hatch out in their nest you may be able to graft them back to the hens... some hens will take them only if a few days different and some will take chicks almost any time, but those are the exception. If there is more than a day or two difference though you need to supervise more closely to make sure the little ones are able to 'keep up' to the older hatchlings and that the broody is taking good care of them.