I ended up in a managerial position at my company somewhat against my wishes due to various circumstances and I don't know how to reconcile this with my leftist beliefs. I do what I can to give my team raises whenever possible, and encourage everyone to take as much time off as possible, but I can't help but feel like a traitor to the cause. I have a mortgage and a kid on the way so leaving this job isn't really an option, but how else can I be a ally to the worker movement?
Don't protect the company interest vs. workers and I don't really see a downside on a personal level. The evil of being a manager is that it typically means you're expected to help the owners seek profits by keeping wages low, getting more production per investment, helping break labor organizing, yada yada yada. But there's enough corporate bullshit out there that you might be able to avoid all of this for ages. The likeliest situation to put you in a predicament will be decisions above your head to fire / lay off. That's the point at which you might feel better about yourself if you stick your neck out to fight for your coworkers.
What matters isn't your label, just your relation to production and how you treat your fellow workers.