I believe dog temperaments are as varied as humans.
I have been around dogs all my life- a groomer over 25 years, shown and trained dogs in agility and conformation, worked as kennel help, vet tech, foster, pet sitting, dog walker, grooming competitions, shelter work, adoptions, assisted whelpings, and pet artist (trophies for shows) of various mixed and purebreds.
I have seen dogs raised from the same litter all different breeds and sizes, being nasty as hell and sweet as pie. Raised and bred identically. Blood thirsty cockers, springers, and collies. Sissy, whimpy GSDs. There goes the "there are no bad dogs, but bad owners" theories, although there are A LOT of bad owners out there.
Homeowners insurance raised in the 90s because I had a doberman and they considered that breed to be a liability, although their statistics shown that 80 percent of bite cases were black labs, yet these were not considered a liability.
For family dogs, I recommend getting the dog from a young pup, regardless of breed/mix.
If you don't have time to train a pup, you won't have time to behavior modify/train any unknown problems this dog may have. Nips from a needle toothed pit pup don't have the same impact as the bone cracking hyena -like jaws of an adult that could scar your kid's face and ruin future prom pictures.
From my observations, the best "first" all around dog for the kids would be a beagle.
The most versatile larger dog I encountered were Standard Poodles. To put up with hours of tugging and painful matt removing all over their bodies from a stranger without so much as a wrinkled lip is impressive. Shave 'em down and you have a great field companion and retriever. Groom 'em up and you are sure to get noticed around town. (One person I know had one as a chic-magnet, lol, used to take it out every Sat to the flea markets and was always surrounded by a crowd of ooh and ahhers)
On the other hand, Chows were often refused at the grooming shops because they bite first and ask questions later, don't like strangers handling them, and give no warning before they strike. (I have met exceptions to every breed and knew some wonderful Chow Chows) I was also leery of a few Pits, Rotties and Afghans for nail trimming, but the nice ones far outweighed the time bombs.
Nowadays, there are many opportunities to foster, which can be a "try before you buy", and know many people who had success with that route.