When my boys were that age playgrounds and sidewalk chalk didn't interest them. At that age they were allowed to wander in the CG as long as they stayed next to each other. No swimming without mom or dad. A good ball seemed to attract other kids for kickball or four square. Capture the flag is always fun, especially if you invite a few neighbor kids and parents to play. I taught them how to use a compass and would hide something for them to find. Geocaches can occupy time, too.
By age 12 my kids were more interested in spending time with other kids.