Finally, you could kill the five workers on track #1. It would keep the kid and random civilian alive, but still have the revolutionary. The evil-at-heart workers were going to die anyways. However, the bloody revolution might actually result in less total deaths on the grand scale because the five workers were explicitly stated to be going to die because of their horrible working conditions. If the oppressive company owner and similar are overthrown/killed, then it would mean that this constant rate of horrible deaths would stop and just be a lump sum in the form of revolutionary war casualties. Additionally, the evil demon manipulating the company owner would be left powerless, as powers of deceiving people will not work on a nonliving object, thus resulting in the main leader of the new socialist country being immune to the corrupting force that was manipulating the bourgeois. He might even be able to defeat the demon by being immune to being charmed and seeing that he's behind the oppression, and thus be motivated (as much as a machine can be) to execute the demon with some kind of task force.

So I'd pick "kill the workers for a workers' paradise".

There are 5 options: Let the trolley run over the five guys on the 1st track, let the trolley run over the underemphasized person on the 2nd track, let the trolley run over the happy kid on the 3rd track, stop the trolley with the robotic socialist revolutionary, or throw the bomb that would ruin everything and just remove a minor annoyance at best. I'm not going to address the last one since it's just a punchline and obviously silly.

Killing the child would mean that the robo-revolutionary is fine and his bloody revolution would likely result in the death or imprisonment of the exploitative company owner, mostly negating the art benefit (aside from his compositions) and entirely negating the increased exploitation. Additionally, since the workers are alive and wouldn't be put in slave-like conditions, they would have opportunities to kill kittens and people and just generally spread misery and death.

So letting both the socialist and the workers live would result in the workers gaining the opportunity to kill for laughs. The motivation for killing the child would be to maximize the amount of lives saved and have a quantity>quality happiness thing going, but that falls flat since the workers would gain the means to cause suffering and/or death in more people than would be in any of the options aside from potentially the bomb.