This is not the best solution, but I've done it, with a reflective vest and a blinky light---run the roads, even without a shoulder. W Wilderness Rd over to the campground should work then run the loops of the campground. I'd stay off World Blvd, but I've included Vista Blvd and Bonnet Creek Parkway as part of getting around Port Orleans for a loop, OKW to SSR to Springs and back. It sucks, you'll occasionally be in the grass for safety, but at 4:30/5AM there's not much happening anyway. I've done 17-20 miles that way.
I've also done up and down every single lane of a parking lot to get 3 miles in, so I'm probably not a great advisor for enjoyable running routes!!