San Antonio is always lovely to visit at any time of year. I can't remember anything specifically spectacular about their New Year's though. Of course, my hubby and myself are homebodies that night. But definitely a very lovely city to visit. Seems like it might be a bit outside the driving range that you mentioned, but doable.

If I wanted a BIG party city, I'd probably aim for LA or San Diego. I agree that Vegas would not live up to its potential with children in tow. If I just wanted someplace different, and maybe not quite so crowded or intimidating as LA, I'd head for San Antone.