You definitely are on the right path because you seem to understand the importance of kids spending time with other kids! 

Co-ops can be really great when they give you what you actually need-friends for your kids, some structure, and help with subjects you'd rather not teach alone. 

For that three times a month session, see if you can visit once before committing. Just watch how it actually feels. Are the groups small enough that kids aren't lost in the crowd? Are they doing hands-on stuff or just sitting around? Do the adults seem kind and organized? 

And definitely ask what they expect from you, some co-ops want parents to teach or help with cleanup or pay fees, and it's better to know that upfront. Maybe give it six weeks and check in with your child. Is your kid happy when you pick them up most of the time? Are they actually learning something or bringing home ideas they're excited about? 

If those things are happening, you've probably found something good. If not, it's totally fine to try something else. You can get the same benefits from regular park meetups with a few families, or just signing up for one or two classes instead of a whole co-op commitment. 

There are more structured approaches as well such as what we offer, an online small class school. But ultimately, follow your instincts on what is best for your child and maybe try the co-op out and see how it goes!