Three factors to consider:-

• Are these cats native (or naturalised) to your local ecosystem? If wherever you live has had cats for a hundred years or so, the local wildlife would have adapted to them. Otherwise, cats can damage the local ecosystem.

• Do you rely on the cats to suppress vermin (rats, squirrels, small birds, etc.)? Even if your cats aren't actively killing them, their mere 'patrolling' can drive these pests away. But if you keep them indoors, you lose this protection.

• Are there any local predators that are particularly good at catching cats?

If your answers are yes, yes and no, then let your cats out. If they are no, no and yes, keep them in as far as possible.

Obviously there's the safety aspect of keeping them indoors, they usually live longer. Aside from that, they're also extremely efficient killing machines. The damage outside cats do to native animal populations is huge.

Unless you live in the native original range for cats, and your local region has zero automobiles, and you have no issue paying vet bills for random illness or parasite infections, then sure. Its probably not that big a risk to let your cat out unsupervised.

Brits are very arrogantly incorrect about their cat care. They are driving local wildcats extinct, and feeding their pets to local foxes, badgers, and car wheels.

You can still supplement outdoor time for your cat tho. Harness/leash training isnt too difficult, just go in areas you dont expect dog walkers. And you can also build catios, outdoor spaces that are fenced in.

Outdoor cats are the number one killer of native species. They have contributed to the extinction of numerous species. Not to mention there are coyotes, cougars, bears, and hawks that can harm or even kill your cat. Outdoor cats also are a vector for diseases and parasites that can seriously harm them, or humans.

Pets should be kept indoors, for their safety, for the safety of the environment, and for your safety.

If you are in the US or Canada, you should know that about half the diet if coyotes is house cats

Cats are actually in more danger on quiet roads than busy ones. Busy roads teach them that cars will always be there and they avoid them. Quiet roads with infrequent cars they don't expect them so they get used to crossing without looking or sunning themselves there in the summer.

There's also people with barns who maintain a constantly churning population of cats to keep rodent population down.

I suspect the middle of nowhere might be worse given that the wilife there might not see a lot of cats normally and could have more vulnerable populations. Probably depends where you live, but if it has rare wildlife you don't see much elsewhere your kitty is possibly bad news for them. Also depending on where you live the wildlife can be dangerous for tje cat too. Eagles and snakes are a worry.

Afaik, the best is to give them enough space but it should be enclosed. They pose a threat to wildlife to some extent, and some of the wildlife can harm them, besides an obvious possibility of being traumatised or lost.

Not all cats are killing machines but with 3, chances are at least one of them is. On the other hand, an outdoor life is probably much more fulfilling for a cat.

At a minimum, make sure they have bells around their collar so it warns the local wildlife.

There's one theory that outdoor cats could be what allows the avian flu to become transmissible to humans which would cause a worldwide pandemic comparable to the black plague in terms of death toll. So there's that.