Swimming is another very good activity to get them involved in. When my daughter was 4 she was still non verbal. Once I enrolled her in a regular class I saw beautiful improvement within 2 months. The motions in the water, water going in one ear & out the other, as well as the breeze her body felt when diving off the diving board all released excess sensory. That in return helped her become much more receptacle. And picked up on the other kids communication skills!
At this period of time she was MUCH less social. VERY timid and shy!! Here again that push they need comes in good and handy. I put my guilt on the back burner and used LOTS of encouragement. Now she's a social butterfly!

Six years ago I enrolled my daughter into Jazz class. She always loved music, who doesn't? Anyway, yes the first few weeks she needed a bit of a push. But after learning the routine she did fine. Don't forget dance is OT and Socialization all wrapped into one! Big turnarounds, positive outcome! Good luck!

I don't know of a particular program near you but what I do when looking for a program for my son is I call them explain my son's needs and set up a one in one consultation so they can see what my son is capable of and what if any class they offer would be a good fit. Most places will do this for free.

I would say give it a try both ways , a small group and 1: 1 . It also depends on the teacher . I had my son join a swim class in India which was a disaster and he never wanted to go in pool but now we have some 1:1 class once a week and he waits for his class the whole week . I did told them about the special needs .

Please check the Provider Directory to see if their are any dance classes mentioned in your area.
I am also sharing this link:
https://www.autismspeaks.org/resource-guide/by-...
You could check to see if there are any YouTube videos to teach dance.