Will pray for you. Good friendships don't happen overnight, they take time and almost a courtship process. Be patient and use the time to connect with eachother in deeper ways. My husband and I recently did a little couples counseling as a marital "tune-up." It might be a fun time to do something like that, especially as you go through these changes in your family life.
As for starting a group, I will tell you one of our closest friendships we have is another Christian couple who have a daughter with Down Syndrome. I said above that dear friendships can take time to develop, well, in the instance of our new-ish good friends, we bonded instantly over Down Syndrome. So, I will say, go for it! You never know who else is feeling isolated by having a child with special needs, and needs that connection with other parents who are dealing with a child with differences. You might just come away with a beautiful new friendship in the process!
Kim. Wife to Ray, Mommy to Charlie (DS), Calvin, and Miles.