For a trip out to a park that combines the feel of a great historical museum with wonderful hiking, try McDaniel Farm Park in Gwinnett County.  This farm housed sharecroppers from 1913 to 1941, and it has been beautifully restored.  Suburban kids will get a great sense of the bustle of the barnyard and the closeness of the natural world.  A large acreage of woods surrounds the park's center, providing peace and isolation from the surrounding malls, and a creek tumbles through the middle of it all.  The URL that I've provided also lists the classes held at McDaniel Farm by Gwinnett County's Department of Parks and Recreation.  Remember to bring a snack if you try the longer hikes - the land drops down into a deep valley along the creekbed that a perfect place for a picnic.