I volunteered at an animal shelter while I was in middle school, back in New England. On the one hand it was tremendously rewarding to help the critters --I like critters better than humans, anyway-- but on the other hand it was difficult seeing the abuse cases, the critters too sick/too badly injured to save, and the critters brought in for euthanasia because their owners had decided the critter was inconvenient. The vets and staff were awesome (probably because I was a little kid), but I can't say that I did much interacting with any humans besides them (probably because I was a little kid). So volunteering with an animal shelter would definitely ease you into large-scale human interactions, but it might come with some depression as you witness critters in unhappy circumstances.
All that said, I like your idea of volunteering as a way to increase interaction. I don't know that I'm up for it yet myself, but I'll keep it in the back of my mind should I ever progress that far.
And indeed, all the very best of luck in your recovery!