Welcome to the RTA Forum!

I'd say your insticts are right, this is a trip that you'll need at least 3 days for. 2 Days would require you to really push yourself to your physical limits.

You didn't give an exact starting point, but figuring New Orleans, you're looking at 1800 miles. Even at 3 days, that will require 10-12 hours per day on the road.

As far as places to break up the trip, I'd actually try to get farther than SA on your first night. Kerrville, TX would be about right. I'd also not try to get as far as Tucson on day 2. I'd be looking more at places like Lordsburg, NM or Wilcox, AZ.

Check out the Art of the Speed Run, and Safe Driving Distances in 1 day for a little more reading on the subject.

I'll also say that while there is nothing wrong with a mom/daughter trip, if your daughter is 20 years old, there really is no reason she couldn't make this a solo trip. It may even be more what she is looking for. This thread goes through the planning and execution of one woman who was very nervious about the thought of doing a solo trip, but happily told her tale at the end of it.