Need suggestions for special child

I received a note from someone seeking advice as the home school teacher of an 11-year-old boy. He writes,

He was born with an extremely rare genetic disorder that makes him a fairly unique case. He's not mentally retarded, but he's very far behind in his language development because he was unable to hear until about age 8 (he hears fine now with hearing aids). He's at a mid-fourth-grade math level, but a mid-first-grade reading level because he started learning to read just last year. He has somewhat short stature, a somewhat large head, large eyes and a small nose---other 11-year-olds might describe him as funny-looking, but I wouldn't say he's desperately so. His voice is very nasal and he has an odd speech impediment, but he's talkative and can be understood relatively easily.

He's outgoing, kind, humorous, well-behaved, and well-adjusted.

Since he's home-schooled, I want to find opportunities for him to socialize. I suspect that groups of non-disabled 11-year-olds would tend to disinclude or bully him because of the way he looks and sounds, so I'm most interested to find groups or activities for kids with special needs. (Or, if there were a "mainstream" venue for socialization that could assure he'd be meaningfully included, I'd be interested in that too.) Sports and music come to mind as good activities for him, but I'd be open to other ideas.

If you have any general ideas, please comment. Specific ideas for lower Manhattan are especially welcome.