I'm originally from the North-East and now live in the south. SO, my Southern History expertise isn't necessarily where it should be. I love when I get to have an educational experience along with my kids! And this happened on our recent beach trip to Gulf Shores.
We were visiting in October and had a cool morning. While we waited for the beach to warm up, we spent a morning exploring Fort Morgan. Fort Morgan is a masonry fort built between 1819 and 1833. Standing guard where the bay meets the Gulf of Mexico, the fort played a significant role in the Battle of Mobile Bay in August 1864. Used intermittently through the Spanish American War, World War I and World War II.
This old fort has a small museum that takes you through the history of the area and how it was used. I recommend doing this part first (it's also where you pay, so that's convenient) so when you walk into the fort, you have an idea of what you are seeing.
The ruins of the fort are ripe for climbing and exploring hidden areas. Other than some VERY steep stairs, this fort is absolutely doable with kids of all ages. In fact, older folks will probably have more problems than the kids. There are notes posted throughout the fort explaining what you are looking at and how it was used. Great to read through and talk about with 8 yr olds and up.
The Fort is conveniently located near the ferry to Dauphin Island. Once you've had your walk through the fort, take the ferry for a view from the sea!
You'll get your history lesson, exercise and fresh air all in one go!