As noted in other posts, every port will have a complementary tour. Some ports have more than one. As an example of the different levels on a Tennessee River cruise last summer, there was a complementary tour of the Quilting Museum in one port that ACL paid the entry fee for. There were low-cost premium tours of Lookout Mountain and The US Space and Rocket Center in other ports. We did not go on any Signature tours on that trip, but an example of a signature tour would be like the Anan Bear Observatory in Wrangell Alaska.
You probably know this, but there are no kid programs on these cruises. Based on the one we were on, 60 and up are the usual passenger age. If your family would not be comfortable just watching the shoreline go by on some days these cruises may not be a good fit.
Having said that, we are going on another one in June, so ACL does do a lot of things right.