I'm not a big fan of letting them work it out / set boundaries on their own. My worry isn't so much that the cat will get injured but rather ending up with a dog who can only see from one eye. Cats are just too damn quick with the poke to the head and (my) dogs are too dumb to get the message.
We will let the dogs play with Gracie as long as they are gentle (all of them, not just the dogs). Actually it tends to be Jack who she plays with - Lucy still scares the bejeebers out of her at times. Once one of them starts to get to rough - Gracie hooking the razor blades into his head or Jack getting nippy, we'll separate them, otherwise will let them play.
Cheers,
