It would seem to me that a fairer way to handle it would be to notify all participants that they would be asked to immediately leave if their dogs were off leash or causing other problems such as barking while unattended. However, I understand that people would complain and might get argumentative if you enforce those rules, which would be an additional hassle for you that you would just as soon not have to deal with. I can't blame you, as I am not a very confrontational guy myself, and wouldn't like to put myself in a position of having to enforce rules people are likely to object to.
However, my dog has always been along whenever I go shooting, and like Scott, I would be unlikely to attend events where she was not allowed. She is trained to stay by my side, with or without a leash, but having to keep her on a leash would be a reasonable compromise to leaving her at home. She doesn't mind; when it's time for me to shoot I just drop the leash and she just stays there anyway.
However, as I said before, it's your tournament and you have a right to set the rules, which don't necessarily have to please me, especially since I couldn't attend it anyway. I do appreciate that you're trying to get the word around in advance, so people are not caught showing up and then having to go home because they have no provision for taking care of their dog while they are shooting.