We played the launch pad on saturday, when we got there (too early) the golden west had LOTS of kids in there, probably the most people I've seen in the Golden West in a long time. So based on what I saw it looked like the bands had at least a good sized crowd to play to. I'd say it might be worth lookin into...
I have never seen the place more than 1/3 full, but maybe that is just my luck. You could probably do alright with an all ages show, especially if its on a weekend. The stage isnt all that bad either.