Austin
If you are going to be in this part of Texas in April, you have a wonderful opportunity to visit Fredericksburg to see the Bluebonnets. Maybe you have a good reason to visit Austin, and there are many good possibilities for things to see there. On the other hand, it is one of my most dreaded cities to drive through, especially with an RV. In fact, I go far out of my way to avoid it on my visits to the Hill Country of Texas.
April is also a great time to visit "our part" of Texas--northeast around Tyler, Longview, Nacogdoches. We have some really nice state parks such as Tyler, Caddo, and Daingerfield--just to name a few.
You can make a visit to Texas a highlight of your trip and not just a necessary drive--and a long one at that.
I have a good bit of experience with your route from Augusta to Texas, so let me know if you have any questions about a specific area or stop along the way.