Hi A.,
I live in the same area (off of E. Cherokee). There is a great park on Rucker Rd, right where it turns into two lanes going toward Alpharetta. It's called Will's Park. It has a total of three playgourds, a great walking path, and then ballfields. One of the parks is separated by age range.
There is also a park being built on Canton Hwy - it's called something like Bella Industrial or something....It's right after the ballfields on your right (actually, you could probably get to it by going through the ballpark).
Other than that, I'm new to the area, so that's all I've found so far. If you want to get together sometime, let me know. I have a 10-month-old who loves to swing!
Hope that helps!
A.