I just came on to say that, however you go about acquiring your dog - rescue centre, reputable breeder, etc, and whatever breed you go for, dogs are individuals just like people and there are simply no guarantees.
My husband's best friend owns our dog's litter mate. Both acquired at 16 weeks from the breeder (both had been purchased then returned - long story), both raised in a very similar way (they accompany their owners in their day-to-day work, and get lots of outdoors exercise etc, both men are responsible owners who have had lots of dogs of various breeds before etc) and you would struggle to find two dogs more different in temperament - ours is gentle, kind, somewhat lazy, and our friend's is a much more fun, flighty, and somewhat naughty dog. Both lovely and loved, but very very different.
My family member, now she is on her own, decided on a Labrador puppy from a reputable breeder this time, having had rescues who were "challenging" breeds before. She knows loads about dogs - used to work with them in fact. This Labrador is ruining her life! It's destructive, can't be walked off the lead with any degree of confidence, boisterous, I hate to say it but really quite hard to like! (And I have always loved all dogs.....)
Whatever dog you go for, it will have its own personality and it's own ways, and you have to be ready for that, if that makes sense?
Which is not to say you can't minimise the risk by choosing a breed whose temperament characteristics tend to match what you want. And you have to put the safety of your kids and your other pets first, so yes of course you are right to make what seems to be the most sensible choice for your family at the time.
Just go into it knowing that there are no guarantees. Not all labs are fun loving family favourites. Of course, good training helps massively, and it sounds like you are putting a lot of thought into how you will raise the dog, which is great.
But even so, there are no guarantees - just like having a child! You never know what you'll get - you have to be ready for anything.....