any attractions/exhibits I shouldn't miss?
I have only been to the Montreal Gran Prix, but Austin should be similar enough.
There are usually lots of "support races" at the track on the same weekend as F1, so lots to watch especially Sunday morning.
In between sessions (Definitely attend Qualifying as well as the Race), you can probably wander around and find the garages for the support races without need for a more expensive pass like for the main paddock. Their owners will likely have them up on jacks for display and whatnot.
There should be continuous entertainment and freebies etc.. on the infield as well. So just go for the entire days (Saturday and Sunday) and soak it all up.