Take that, Lollapalooza!
And just as with Lollapalooza, there are a good 30-40 other artists worth your time.
The 2006 edition will be held Sept. 15 - 17. And, as an ex-longtime resident of Austin, I can assure you that it could (OK, will) be just as humid as Chicago in early August. But the pace is much more relaxed. And you're right around the corner from Chuy's Barton Springs location...
(Of course, I post this knowing that the idea of families flying to Austin for the weekend for a concert festival is a bit, erm, far-fetched for all but the most devoted and affluent. But still.)