Hi Elis,
It's a bit late now admittedly but I'd say if you felt comfortable enough (i.e not an open office) then it's worth coming out, if only to educate the person you're dealing with*. I feel like personally, the biggest issue I've had about telling people I'm non binary is that they tend to forget very quickly and just reassume binary pronouns and behaviour (in my case to assume I'm female because alas no hormones) which can be irritating but doesn't exactly extend to bullying type behaviour or discrimination (unless you count ignorance) so to me there isn't a massive downside to coming out. Of course I don't deny that once people get more 'informed' about non binary identities they will be more likely to be outwardly discriminatory or hostile (as they might be towards binary trans people) even though they may also be more likely to be accepting or understanding. Funny how that works :/
I feel like the biggest hurdle for me, being non binary in a workplace environment, is the fact that people don't even acknowledge it so personally I would want to make a point of mentioning it. Also, if you work somewhere every day and are getting constantly misgendered then I feel like that would make the job very unpleasant. I may be too sensitive though... I appreciate that if male pronouns are somewhat acceptable to you in certain circumstances that it would be a price worth paying for privacy in that regard.
Have you been to the volunteer agency yet? How did that go?
*eta: obviously anxiety/general mental argh can make coming out difficult or unwanted for a number of reasons and not meaning to belittle that. I also have brain gremlins that make me want to stealth it and that's ok!