Do you free feed your dogs, or are they on a feeding schedule? We have a scheduled feeding time, and we have to supervise to make sure 2 cats don't force the dogs out of the bowls, but we do leave some out later at night for a snack for them to munch on.
BTW, dog food won't hurt cats but cat food will hurt dogs. If the cats get into their nightly snack, I don't worry about it, but I do have to fend the two cats out of their dinner (they love the wet food!).