Although I have a daughter, she's the same age as your son, so i hope i can help. Jen does GirlScouts and tumbling class. For GirlScouts, there is also a young girl in her troop that has Turrets. The troop knows that Jenna and this girl are different, so Jenna is actually doing a presentation on the Autism spectrum and what makes her a little different. :) Girl Scouts has really been a great outlet for her. She's also made friends through her tumbling class. ALL the kids in there are running around and being silly--she fits right in. I doubt any of them even know she's different--unless, of course, she's brought up cheetahs (her specialty). :)

I get together with other families who have older and younger kids..having a sibling with autism helps the neurotypical kids respond to mine better than kids who aren't familiar with autism.

Ryan and I moved around a lot for 2 years, so the first thing I did when I got to a town was find the local library. I picked up their schedule of events each month and signed him up for the activities.
The other thing I do is find a local park (with a dog park) so he can play with kids or dogs while I meet other adults. We've even driven around our area and found small neighborhood parks, that get busy before dinner, so he can play. Also, check out the YMCA, they have lots of activities and even going and watching the older kids practise team sports has been a good time for him. Lastly, join a bigger church even if it isn't your religion. They have great Sunday schools, so he can be amongst his peers, do a craft, and have a snack. I even had him attend the Bible Summer camp and he loved it! I hope these suggestions help, it has been one of my main concerns, as I'm an older parent too, and I didn't want Ryan to be a lonely "only" child. :)

Does your son have any cousins his age? It might a starting point since he knows them and vice versa. My son is five years old and his playdates are with typical kids but I find the playdates more successful if they are structured and I act as his speech therapist and help them facilitate conversation and redirect my son if he starts to lecture on a number of his obsessions. It's a lot of work but communication and joint interest are key to repeat playdates. Back to where to find playdates, can his teacher recommend any peers who might be good matches, especially if he/she knows one that has similar interests. If you belong to a church, talk with the youth group coordinator re kids in the group. Older children are better at scaffolding conversation so if you have friends or family with any, they might be good matches.

Any STRUCTURED activity will help your child interact effectively with non-Spectrum kids; sports, scouts, etc.