Road trip - Charleston to St Augustine with toddler
 

Good morning - My husband really wants to do a roadtrip from Charleston to St Augustine but he doesn't any idea of exactly he wants to see and do. I'm not from the States so I can't really help him figure it out either. I don't even know if this is a good idea to do with our toddler (18 months). We really need help with a suggested itinerary (10 days max).
thank you so much in advance!

That isn't very far and there is lots to see in both terminus cities. Have you been to other places in the southeast that you would also like to visit?
In Charleston there is a nice aquarium that your toddler would enjoy. Walking tours of both cities would be good with a toddler in a stroller. An 18 month old is certainly capable of travelling with time outs for a nap and a nice waterfront place to have lunch to entertain him/her.
10 days in just those two places would be a LOT IMO so veering off to nearby places could be good. What time of year will you be traveling? The beach in the areas would be a nice diversion--spend some time building sand castles and if summer jumping the waves.
We need more information.

En route to St. Augustine you could stop off for a couple of days both in Savannah and Fernandina Beach.

Fernandina Beach. Charming Fernandina Beach on Amelia Island has 50 blocks of historic buildings housing restaurants, bed ‘n’ breakfasts, and boutique shops. Check out the cozy Book Loft, a famous independent bookstore (it has 1,500 rare books). Ft. Clinch State Park features serene beaches and six miles of natural surface trails for hiking and mt. biking. You can sail the islands aboard a 100’ replica 19th Century schooner (sunset cruises).

Latehortua4115

I think that sounds like a potentially delightful trip. Something like 3 days in Charleston, 3 days Savannah and 3 days in Saint Augustine, stopping perhaps in charming Beaufort between Charleston and Savannah for lunch. I like the idea of the stop Prairiehiker mentioned too, although have never been; there are actually a few places that have piqued my curiosity between Savannah and St. Augustine, so do report back if you check out that area a bit.

While part of what I enjoy in all is visiting the museums and historic homes, which might be tricky with a toddler in tow, I think there are things one can do in all that might work. In Charleston, Fort Sumter might be fun, with dolphins potentially to be seen on the boat ride out. All three cities have beaches in easy reach. Strolling through the squares in Savannah would work and Fort Pulaski may be worth a detour, slightly outside Savannah. St. George Street, the Castillo San Marcos and the significantly outdoor Prince Murat House complex (Napoleon’s nephew) in St, Augustine might work well. The Fountain of Youth Archaeological Park in St. Augustine was a bit cheesy but I could see being possibly fun with a toddler.

Best wishes

Daniel