Once your group gets the hang of having a civilized conversation try adding another activity. Play a board game once in a while. I taught a group of middle school kids with ASD to play YAHTZEE. I had no idea how much fun we would have. They loved it! They were helping each other choose what dice to keep, they worked on math skills and didn’t even realize it, they practiced taking turns, they used inside voices and they learned how to be graceful winners and graceful losers. It was amazing.
One student was having trouble keeping her dice in the cup. Every time she shook the cup full of dice the dice would fly out of the cup. Her friend next to her had the solution. He took the cup with the dice inside and covered the top with his hand. In his best James Bond type voice he said, "Here Betty. Try it like this. Put your hand over the top and shake it like a martini."
You may already be playing board games with your kids. Work on social skills at the same time. Play Monopoly. This is great for kids who have trouble understanding the concept of money. If you don't have time to finish a game of Monopoly give everyone an envelope to put their money, token, properties etc in. Write their name on their envelope, put the game away and begin where you left off another day. This shouldn't bother your kids at all. They are from the video game generation. They put their games on pause all the time.
The most important thing to remember is to have fun with your kids. When you practice these skills in a variety of settings it helps them bring what you've taught them into all areas of their lives. Encourage them to try the things you work on at school. Ask them how it went. Discuss what they could try next time.