Such a great city! Two major things there: eat in local restaurants and listen to live music! Visit a big bbq place, many caters to groups. My favorite bbq place on earth, The Salt Lick. https://saltlickbbq.com/venues/
they have two places in the Austin area. Go. Will not disappoint. Also the Magnolia Cafes in Austin are all night restaurants with great inexpensive dishes. Both in the city, very local. http://www.magnoliacafeaustin.com
The East Austin area has becme has become the Brooklyn of Austin. They have great food trucks and local places.
Music is all over but I really like Threadgills for a a live us I show, they have a good outdoor theater (and indoors I think). Never ate there, just saw concerts. http://www.threadgills.com/calendar-world-headquarters/
Look into air bnb for staying, as you are a group. A car is good, but Uber & Lyft are as well. And scooters...they are all over, I hear.
Hope this is a good start!