When large dogs eliminate, they eliminate a lot more than small dogs. More goes in and more comes out of large breeds. Which is something to keep in mind if your dog will live inside - especially if you live in a high rise apartment and he will have to be litter box trained (there is always going to be more to clean up).
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.
All puppies are cute, but some breeds have that extra “je ne sais quoi” that makes them irresistible. For this reason, some of these breeds are popular in greeting cards, commercials and other marketing materials.
Some breeds have so much energy and are so active that if you do not give them a sufficient workout every day - a long walk and hard run - their pent up energy will quite likely manifest itself in destructive behavior.