In Fredericksburg, the Admiral Nimitz museum is supposed to be fantastic. Outside of town, the LBJ Ranch and Park is interesting. There are lots of wineries in fredericksburg if your college student is of age to drink where you can do wine tastings that are always lots of fun.

Don't miss Enchanted Rock.

http://sculptureranch.com/- Benini Sculpture Ranch- a place I have been wanting to see.
http://www.longhorncaverns.com/- Longhorn Caverns
http://www.batcon.org/index.php/get-involved/visit-a-bat-location/congress-avenue-bridge/subcategory.html- Congress Ave Bridge for bats
http://www.pacificwarmuseum.org/index.asp- Adminral Nimitz Museum

There is just so much to say about that part of TX. I love the food- all sorts from great Mexican,to barbecue to different ethinic choices. The cities have so much to offer. Go on this site for Austin information: http://www.austintexas.org/visitors/plan_your_trip/

Have fun there!

You leave in 3 days or you have 3 days total to travel?

Just curious where you are taking the kid and is this trip after you drop off the kid? If you are dropping off the kid perhaps in Austin, then yes, head to F'burg, visit a few wineries on the way from Austin. My fave is Becker. They have a fun tasting room. For me, one day in F'burg is plenty. You can spend the night there (unless there is a special event on a weekend, then most require 2 or 3 night minimum).

One night on the Riverwalk, visiting Alamo would be good.

With that said, you could base yourself in Austin and make a da trip to F'burg. Agree Enchanted Rock is cool- but all this depends on what your interests are?