My grandparents lived on a farm and kept cats in the barn as mousers. We had a dog, as well, who stayed outside during the day in good weather but was brought in at night and in bad weather. She had a house outside too. My mother tells me this was because the dog was mine. Purchased for me as a toddler when it was a puppy, but that when she was growing up animals were not allowed in the house. It's different in rural areas. However, my experience has been that the city is much more dangerous for pets, especially cats. Many are struck by cars. I live on a greenbelt next to a drainage canal (some call it a creek) and we have.. bobcats and coyotes roaming it and into our yards, as well as Hawks and owls. Many keep owl houses to curtail the rat population, but they also get small pets. So, it simply isn't safe for cats or small dogs outside. Several dogs have been taken by hawk right out of their own backyard in front of the owner, so you cannot leave them alone even there. Likewise bobcats have jumped fences to get to a dog.
We have had cats in our house for nearly 50 years now. Our first was allowed to go out and came home constantly with an injury or illness (worms, fleas, disentary, tears and bites...). The vet told us cats, (once used to it) are quite content to stay indoors. So, from the second cat till today we have kept them indoors and they do seem quite happy. In fact, the one I had for 19 years didn't want to go out at all. I would take him out to sit on the porch with me and he would run back to the door and cry to be let in. So, I believe in erring on the side of safety and keep cats in, let dogs run in the backyard, but if they are small, keep an eye on them. This doesn't even cover the dangers of cruel people. As if nature wasn't bad enough there are evil people out there who at best will steal a pet and at worst I hate to think about. Don't ruin the fun memories of your trip by coming home to something sad about your fur-babies. Peace of mind is worth a lot.
This post was about leaving pets when traveling and if you love your pets like family, then think what you would do if you had to leave your child. Never leave an animal alone for days. He could get into something harmful, here in Texas we have sudden horrible storms that can really frighten them at best, but could do damage to property and you wouldn't want them out in that or in a house that was damaged.