Personally I think it'd be a shame if one regrettable incident caused a blanket ban. I have absolute sympathy with the child & child's family of course and there is no excuse for having an unreliable uncontrolled dog in a public space frequented by vulnerable children. But... so long as dogs are controlled and friendly I like having them around at festivals even though I don't have one myself. I have sevaral festival going friends with dogs who would not be able to go to places like Shrewsbury if they couldn't take their pets along. How about a "dog's to be kept on a lead at all times" rule (or maybe you have one of them already)?