We took our antique A down the whole trace several times.
Advice:
-Download and print the maps before you even get close.
-If you can find it, buy the book(ISBN 978-0-89732-925-5).*
-Do it at least once in the early spring. When the trees fill out you will be driving though a tunnel and it will be difficult to see the Trace along side the road way.
-Relax, you have 444 miles with no cross traffic at all.
* Visitor centers at MM 385.9 Meriwether Lewis, 266 Visitor center, 102.4 Parkway Information Cabin, 15.5 Mount Locus.
When you find them, get their printed maps to carry and three others to give to friends. Three is enough because there will be new prints before you give out more than that. (They can also download and print their own.)
Nashville to Tupelo is only about 180 miles. There is a lot more to see/do.
There are multiple free/cheap and more than a few $$ other campgrounds, but you have to learn what you need.
Matt