The “Ameraucanas” could be many colors or patterns, so that really doesn’t tell us much. With a Black Copper Marans for a father the chicks are probably going to be pretty black anyway. What the mother looks like probably isn’t very important. There is a fair chance you will have some trouble telling the chicks apart at hatch.
The idea of putting a fence down the middle of the incubator to keep the chicks separated is a very good one. You can also get small mesh baskets or make baskets out of hardware cloth to put over the eggs and keep the chicks separated at hatch. Then paint the toenails with toenail polish to keep them separated for a little while.
Some Marans have feathers on their feet and legs. If their father does, any chicks with feathers on their feet are his.
As long as the Ameraucana hens are not barred, the v=barred rock chicks should have a white spot on the head while the Marans cross probably won’t. That might be another clue.