I wouldn't apologize or refund money..

It's hard telling why the ladies got a bee in their nethers and it's for them to deal with..not the host.

What I would do is send a nice, friendly note (mentioning that I represent myself--not speaking for the band) and a couple tickets..marked "disgruntled patron comp" so whomever is at the door can know to keep an eye out in case disgruntlement is a favorite hobby of whomever uses the tickets.
If the tickets aren't used, the gesture has been made. Who knows, one of the ladies might like to come back without a cranky sidekick.

If you're going to eat $40, it seems sensible to do it on your own terms rather than as response/reward to bratty behavior.