Gordon Biersch is a "brewpub", a restaurant/bar that serves beer brewed on the premises. shouldn't be any problem with you and your son can getting a table and eat brunch while listening. It is a short cab ride off the strip, directly east from Caesars on Flamingo Rd, then a little bit north on Paradise. Maybe a $10 cab ride, if that.
UNLV is over in that direction, and they sponsor a jazz society:
http://vegasjazz.org/
Just looking over their calendar, they have a lot of not-in-a-bar performances.