I think you can make something such as mc dream back in the "past" again like what you did last time, but this time it can be a longer version, here is my idea:
Mc some how dream about the girls in original timeline during his sleep, seeing how they will be in the original timeline facing their own happiness, sadness and problems. But the scenes will fade out quicker and quicker as the more mc changed in the past, the weaker the link between old and young mc, when mc totally changed the future the link of original time will be forever disconnected.
This idea can solve your problem of telling the story of the girls in original timeline, it also can let mc know more about the "future", which in his view is impossible to know, and use that informations to prevent bad things happen.
Hope my idea can inspire you to more greater ideas!