Wow, this is so sad, sorry for your loss. We have two dogs, a Corgi and a rescue doxie. The Corgi is totally chill with the girls, but the doxie went nuts and tried to dig under the coop to get in. Our coop is custom built and sturdy, but the run could be breached if something dug under it. (Will look into the apron!)
Our solution was to put up a barrier between the backyard where the dogs are and the side yard where the coop is. The doxie can't see the coop, so is no longer interested. We also have tree cover in that part of the yard, so no flying predators can scope out the coop (we do have hawks), and while we also have raccoons and oppossums, the dogs will bark if they hear anything in their yard (and we'll hear it as well). So far, even the cat is mostly curious...he doesn't go into predator mode when the girls are out, and our EE scolds him when he gets too close.
We live in a very suburban area, though we do have an open field nearby, which is why we do have some predator load. My theory is, if something REALLY wants to get your girls, and is hungry enough, and there isn't another "alarm", all animals are somewhat at risk. We had a mountain lion in our neighborhood a couple of years ago, and several pets were eaten. Who'd a-thunk?
Edited by SVTechChick - 3/15/16 at 6:41pm