If Mama 1 takes her hatched chicks off the nest, maybe you could candle her unhatched eggs and slip some of the farthest along ones (that look like they are similar in development) and slip under her.
Have you candled them at all? A staggered hatch can be tricky - do you have an incubator and brooder handy, so when the hens take the first-hatched chicks off the nest, you can incubate and brood the late hatchers?