I would do the fenced in area, and connect it to your house around a small dog door - fenced all sides, including the top, and bury blocks underneath the fenced sides (to prevent any digging out or something digging in). That way you can train them to go outside as they need to, and they can enjoy the outdoors a bit, too. No birds, no foxes/raccoons, etc can get to them. If that won't work due to your house set up, then second best is a fenced in/roofed raised 'playpen'. We did that for our yorkies years ago when we lived in an area with cougars, hawks, eagles, etc. They could go outside to do their business, to look around, etc., and we knew they were safe. We unhooked latches once a week, and moved it away from the house and their dog door to scrub and sanitize their pen. Worked great. Left it with the house when we sold it (scrubbed & sanitized, of course), and the new owners put their cat's litter box out there, and so the cat could be outside to watch everything going on.