So, I see Tsunade getting taken out by Flower Tree World (the jutsu was stated to be instant, and although that's a hyperbole it's showing you just how fast a forest of that magnitude is created, and Minato would likely want to have his more powerful ally still conscious to help him fight an adversary with such power like Hashirama).
Then, Itachi and Minato spend their time/chakra reserves on a Wood Clone (extremely durable, and they won't be able to tell the difference between the Wood Clone and Hashirama because it's manga fact that it takes at least EMS to do so).
Sneak attack from the real Hashirama after the clone is defeated in an arduous battle, and even if Minato can react, both him and especially Itachi won't have the chakra reserves to hold out against him.
Hashirama beats them without killing them (they all pass out eventually).