RE: Banana's Foster someplace other than Brennan's?
Dolly, in Austin, go to Eddie V's (specializing in fish) or Dan McKlusky's (steaks) for excellent Bananas Foster. Prices at both are not "cheap", but not outrageous. Since it's a special dinner for your daughter, both would be affordable.
In Austin, there is really no such thing as a "dress code". With the exception of perhaps a few restaurants you could count on one hand, NOBODY has to dress up here. I go to places where my self-imposed decorum forces me to wear khakis and a blue oxford, and there are people in shorts and t-shirts who fit in (right alongside people in suits). "Everybody is somebody" here in Austin, so you'll feel comfortable anywhere you go dressed in whatever you feel like wearing.
If you would like other recommendations for places here (I don't know your route or schedule), just click on "Bushie" to the left and send me an email.
Sounds like a fun trip. Happy Trails.