I just did a quick run-through of it, to make sure I understood. What I did was unlock the door to Springtrappy (by buying the hammer and metal file), did the lewd scene there, went back to check on Mangle, then chose to run to the room with barrels. When I regained control of my character, it was the next in-game day, and the door to the endos was available. The first time you click on it, before unlocking Springtrappy, it introduces them.
It seems like you have to go to Springtrappy and mangle in order to unlock the door to them, to fight them. After fighting them becomes an option, you are able to buy a bat from the security computer.
Also, not sure if it makes a difference, but I clicked on the machine in the room to the left of the door with the keypad, which prompts the mc to mention that the endos could be broken down by it.