What's the point at which social interaction for a group of 2 year olds, is bad versus good? I just feel bad for him, he is a sensitive kid and I'm not sure how much of it he can take without starting to just dislike other kids.
My personal feeling is that playdates are for playing and having fun. I would absolutely not force a 2-year-old to a playdate he didn't want to go to or make him stay for longer than he liked. Honestly, I think kids are not so much into socializing until 3 or even later in most cases. So I wouldn't stress about this at all at 2.
I agree with this completely - both of my kids were daycare kids from 8 weeks old. DS almost 6 actively participated in "extras" like Tumblebus (a bus that came to the school that was made into a "gym"). We attempted to sign DD4 up at 2 (DS started at 18 mos), and she would just stand on the bus and not participate. All kids are different, and socialization will come with age - regardless of the age of the kids. DS socializes more with girls because they are generally more mature at his age - but when he plays with boys, he tends to play more with kids that are slightly older.
I would not force the playdates just yet... or maybe have a "private" one with the 2.5 year old that is calmer.
Good luck!