And you need and indoor activity visit the Augusta Museum of History http://www.augustamuseum.org This place is awesome there are Native American exhibits as well as Civil War exhibits. There is much on the history of Augusta there and things for children to do.
There are also many different collections there from the area. Things from the Native American tribes that lived in the area, artifacts found in the area, furniture, Civil War memorabilia and art. You name it and it is probably in the Augusta Museum. It's a must see to put on your list of things to do while in Augusta.