This issue has happened to me before. I was teaching a combination class in a studio alongside with the owner of that studio. She had a dog, and the dog was always there. Most people like me love dogs and we didn’t mind if the dog was there. But there were a couple of situations where some clients were allergic and scared of the dog. They ended up cancelling the rest of their sessions at the studio because of the dog. So, after that we decided to keep the dog in a separate room when the class was going on and we avoided future problems. Now, if the class is offered outdoors those clients might not mind having a dog there.
I would just let everyone know that there is a dog in your place so they will know what to expect and not have to deal with it after they sign up. Sometimes they might even give you bad reviews because of the unpleasant experience they had at your studio.
Personally I love dogs and I have nothing against them being there :-)!