Labs are incredibly intelligent in general. The very best bomb dog I've ever seen was a lab. He was also the easiest bomb dog to train I've ever seen. He was also the only single purpose (not bite trained) dog in Special Operations at one point because he was such an amazing dog.If you spend most of the time with the dog you should get what you want, if your wife is doing all the work you should get what she wants in my opinion. Labs are usually super nice and cuddly but often not very bright especially in comparison to German Shepherds. Our German Shepherd doesn't like to cuddle unfortunately on the other hand he doesn't go to every freaking person that comes along for cuddles and attention, I love that. We live in the city and we have to go to dog parks to let him loose. In the dog park or on the way there we see a lot of other dogs and when the dogs don't get along the German Shepherd is a lot to handle and if the other dogs owner fails to react you may have to handle 2 dogs going at each other. I've got nipped at and bitten quite a bit by our own and other dogs when they got mad at each other. Your wife and 6 year old would not be able to handle those situations. But if you live in a house with a big yard and you can get him running and exercise there you don't have the issues I'm dealing with. I grew up with a German Shepherd and it's the only breed I ever want.
Most service dogs are labs.
Here's a pic of Marshall, the most amazing bomb dog I've known. I could run him with a radio on his harness, a laser, hand signals at 150m away, and with pulses on a vibration collar (as in 1 for go out, 2 for right, 3 for left, 4 for back and long press for recall).