I manage a restaraunt, and see working dogs come through with some regularity. They don't often wander around, and hardly make any noise at all, really. Several servers were unaware a dog was even under the table for the better part of half an hour, until the tell-tale tail made an appearance from under the table. Some working dogs will get worked up if people start giving them too much attention, but they usually know they're there to do a job.
As pfife stated, I'd be worried about the dog's hearing. The SPLs are bad enough for humans, but aren't dog's more sensative? You said he's been to other shows, and I don't know if there have been studies about dog hearing and sensativity to SPLs, but at any rate, he will be down lower to the ground, so the sound wouldn't be as strong. (we've all bent down to check our gear, it is much quieter down there).
IMHO, a dog in the section would be fine, and I would rather hear a single dog bark over half a dozen baked wookies groaning into the night.