Is it acceptable..?

[Letstryagainshallwe]

For neighbours dog to bark the entire time I'm sat in the garden with my kids?

No

Who wants to hear a dog barking for that amount of time the owners should deal with their stressed dog

And while I might feel sorry for it feeling stressed I would also find it incredibly annoying and would judge its lazy owners

What are you going to do about it OP?
I don;t think us MNers can help you via our keyboards.

If you don't want to approach the neighbour, have you a local dog warden? It's not fair to leave the dog outside while the owner isn't there. I rang ours when a neighbour's 2 dogs were barking non stop for hours on end. They popped round one day, had a chat and the dogs are now called inside every time they get barky. Worth trying? Ours said they investigate every complaint so you might get somewhere, and you can do it anonymously if you'd prefer.

Not acceptable, it's a noise nuisance. If a one off, let it go, otherwise you're within your rights to complain.

Unhappy dog. Tell the neighbours and report

It is super annoying. Throw a massive bag of dog food or a big bone over. I know you shouldn't have to but the dog is just lonely and poorly trained, the family have failed to manage its anxiety, and at this point you're best off doing something constructive to try and recover your day. I can't think of anything else that will shut it up.

We had to report our neighbours to the council (after several people had actually talked to them) because they kept leaving their dog outside whilst they were out all day and anything set it off barking, even my being in my own bathroom and kitchen. Everytime a neighbour went into their garden for a ciggie, there'd be constant barking. Etc.

Not sure what the council said or the neighbours did, but we did all notice the dog was being walked when it wasn't previously.

Oh I've never seen this dog come to think of it. Only ever hear it in the garden. So don't think it's walked very often.