K.M.
I suggest you look into Eastside Mother's & More:
http://www.eastsidemothersandmore.org/
I met mothers of all ages. There are plenty of activities for you + play groups for your son. There is a very active website with something for everyone. You're bound to find a few mothers (there are MANY) who you have a lot in common with and you wind up doing stuff together in addition to group activities.
I'm no longer a member because we had twins and the local twins group is a better fit for us now. But I'm going to brunch next month with some current & former moms from Eastside Mothers & More, and I'm really glad that I joined when we moved out.
Good luck!