In my opinion, the best dog breed for children is a Labrador. We have a three-year-old female black Labrador and she’s delightful. When we were deciding on breeds, we chose a Labrador because of their reputation as being fantastic with children (our other short-listed breed was a [name_u]Golden[/name_u] Retriever, but they shed a lot more than Labs). Ours is brilliant with children and will be great when we have a baby. My advice would be to buy a dog from a registered breeder and make sure (for Labradors) that they’ve had their eyes and hips tested (they can have problems, but won’t if their test scores are good) or, if you choose a different breed, the tests appropriate to that breed. Not all breeders do them, unfortunately. Make sure your breeder breeds for temperament. Our breeder was fanatical about breeding dogs with great temperaments. Our dog wouldn’t hurt a fly. This is very important! [name_m]Don[/name_m]'t ever buy a dog from a friend or from a newspaper. Sometimes pure-bred dogs will be advertised, but they haven’t been bred by professionals and you’ll be very likely to run into problems with health and temperament.
If you get a dog from the pound, they will likely have a good temperament (our local shelter only adopts out dogs who have had their temperaments tested), but may run into health problems down the line (or may not - you never know!).
I don’t know heaps about the other breeds you’ve mentioned, but I’d advise against getting a Border [name_f]Collie[/name_f] as they can be “nippy” towards children. [name_m]German[/name_m] Shepherds can be very timid, which can be a problem when interacting with people and other dogs (they can become aggressive in fear).
A puppy and two small children will be serious hard work! Our dog was full-on for the first six months of her life and, even now, she needs a lot of attention. If you get a bigger dog, make sure you have a big enough garden.
Also, get a female dog! They are better with children and less likely to be involved in dog fights.
Goodluck!