You should probably be upfront about selling the candids. I am guessing the OP will not mind(in most cases) but, if they do, and you get caught by them, they can make things unpleasant

I know other photographers(sports) that will go as far as getting someone banned from the facility for shooting and selling. I don't think that dog/horse show photographers do that as much, but, they might really give you a bad name.

Like any business, it is small and political. I know this is a HUGE issue with equine show photographers. After shooting for 12 hours a day straight, you get pissed when someone comes in and takes a share of your pie away.

David Ramey and Jim Garvey can probably give you better pointers on this. I am ultra worried about pissing off other photographers. I want them to work with me, not against me!