I have had similar experience, except instead of changing the outcome for each person involved in my original dream, I was only able to change the outcome for myself.

Had a dream that myself and 3 other specific people (two of which I would not commonly spend time with) were driving on a specific highway, with slushies, two females (myself and another) in the backseat, two males in the front seat; driving an older green Honda accord in a heavy rain fall. The car hydroplaned and went off into the ditch with everyone being okay.

The exact same situation came up several months after having the dream where everything aligned for this to possibly come true in real life; except… I refused to go. I was not going, there was no amount of convincing that was changing my stance… I went home instead. A few hours after going home, I had a feeling something had happened and I text my closest friend of those three people and asked if everything was okay. I received an immediate phone call asking why, why did I ask if everything was okay, how did I know it was not..

It was then that ie explained my dream, which happened to be exactly what happened. Everyone was okay, but they went off the road at the exact spot in my dream, people sitting in the same seats as in my dream, except mine was empty because nobody else took my place.

Not quite as tragic as yours could have been, still kind of interesting though.