This is only for a few nights? Can't they just splurge on a hotel near the festival and metro? LA is huge...you will find places all over but not suitable or fun for kids for a few days. Arcadia=zzzzzz. Vernon=trucks & factories. You don't want them to waste all of their time getting places.
And give up all hopes of seeing the rare and elusive celebrity unless they go to a TV show taping or something....and that takes a big chunk of time. Old town Pasadena is lots of bars and restaurants is very nice and they can go there in evenings after the festival.