Midvalley never became a Gung-Ho Gun or followed Knives. He's still cocky and self-assured, but a lot less bitter. Also he never killed anyone, though he figures he ended up in hell due to smoking, drinking, and sex. He's still a jazz musician, in fact even more of a musician if that's possible.
In terms of canon, the most significant thing Frank could do would be to keep baby Walter, but since Walter is in this game that could get confusing to work out. So I'm going with my fanon: Frank told his wife Judith to stay in college and did not marry her. In fact he never married anyone or had a son, though he still became the superintendent in South Ashfield Heights. He's a lot more withdrawn and a little "nuttier" but also less serious in some ways.
Eileen never gave Walter her doll, and was never his victim. (This could also conflict with Walter being a player here, but I'm hoping it's OK if we say this is what happened in Eileen's reality.) She doesn't know Henry very well at all except as her neighbor who once disappeared for a few days, though she still thinks he's cute. She herself is more cheerful and outgoing, more shocked by violence, and isn't much of a fighter. (Though if anyone attacked her she could pick it up quickly as she did in the game, I think.)