I am a little bias in the fact that I am an advocate for American Pit Bull Terriers, but to pick out a specific breed for a family pet can be tricky. Labs are great family dogs but they are hyper and tend to be high maintenance (full of energy, need a lot of attention). Golden Retrievers are a favorite among families because they tend to be more calm but still very loyal and loving and willing to play. I just did a hub yesterday on the top 10 dog breeds. You should take a look to see. The numbers are based on registered dogs.
Mutts are great way to go too. I have a super mutt that is 1/4 chocolate lab, 1/4 german shepherd and 1/2 something else (owner of her mom didn't know what the pup's dad was). She is an awesome dog, loyal and protective like a shepherd but playful and bouncy as a lab and a complete water dog.
Good luck, he should also consider dog size. Chihuahua's are not good overall for kids because they have a high percentage of bite or aggressive acts. They can't do too much damage to an adult but a small baby could get seriously harmed.