After you go to the Flying Saucer as you are a young man, go over a store to Brindle's and have some great Gelato. My wife and I do that all the time.
Is it a shotgun shoot, BTW, at the National What'is name center?
The River Walk is fun but touristy. There are interesting restaurants in the city. The local things to do are BBQ or Tex-mex.
I'm partial to Tom's Ribs. Karim's for Tex-mex. La Fogata, La Paloma Blanca. There are many.
Near Trinity - Tomatillo's is good. Van's is good for Asian, Koi Kawa for Japanese.
If you want to shoot - if you have time - check out
www.rivercityshooters.com or the above mentioned Bullet Hole.
If you can go to Austin for music and night life.
If you like brick and mortar gun stores with interesting selections (but can be pricey).
Dury's (my choice), Nagels - lots of stuff (nice knives and pricey), McBrides in Austin.
If you do go to Austin during the day - go to McBrides, Book People and Whole Foods all on Lamar and then stay for food and music.
Oh, I second Chris Madrid's for the burger fix.