If you do not have time to exercise your dog daily with a brisk walk and lots of running choose a breed that does not have high exercise requirements. All of the breeds who require high amounts of exercise make terrific jogging, hiking, and ridding companions. So if you want your dog to accompany you on long runs choose one of these highly active breeds built for endurance and as much exercise as you can throw at them - they will love you for it (and a tired dog is not destructive).
Most all dogs will get along well with children if they are raised with them. However, some breeds have a protective streak in them and may become aggressive with children who get to close at meal time (although this should not be tolerated), or aggressive with children they have never met. These breeds will likely see the children as being underneath themselves in the "pack order" and may try to dominate them.
Today there are over 400 recognized breeds of dogs in the world. Many of them have historical origins dating back hundreds, even thousands of years. Wherever humans have lived, dogs have been alongside them performing various tasks. One of the reasons dogs have been such a successful species is because they are so adaptable. They have made themselves useful in countless ways to humans so we kept feeding them, providing shelter for them, and, yes, breeding them. It’s no accident that we have dogs able to hunt, herd, guard, track, and do so many other things at an expert level. Humans figured out early on that if you bred dogs that were good at these things, you would get offspring that were also good at doing them. All of these jobs performed by dogs were necessary for our own species to survive. It’s no secret that we owe a lot to dogs, just as we do to other animals.
Dog breeds are dogs that have relatively uniform physical characteristics developed under controlled conditions by humans, with breeding animals selected for phenotypic traits such as size, coat color, structure, and behavior. The Fédération Cynologique Internationale recognizes 337 pure dog breeds. Other uses of the term breed when referring to dogs may include pure breeds, cross-breeds, mixed breeds and natural breeds.