I don't think you should adopt a pup right now... I know that your kids want one, but I remember as a child wanting pets and my parents said no, and I understood that and just adopted a pup once I was out of their house. Meaning, adopting an animal is a HUGE lifelong commitment, and children don't understand all the ramifications of it. I don't feel deprived because my parents said no, and now that I have a dog of my own, I don't blame them one bit! They are also very expensive, and our life now revolves around our dog. Many kids ask for ponies as well, but parents have to tell them no... they are still okay! If you kids would love a pet, what about a hamster that they can help care for and watch? Or another caged animal? What about spending time with friends that have a dog so they can play? Children just don't fully understand what it all entails - I'm an adult and I didn't until he was here in my house!
That all being said, if you are still going to consider a small pup, I highly recommend Shih Tzus, which is what I have. Harley has been a joy, and i'd get this breed again in a heartbeat. He's content inside, needs little exercise, travels well, very adapatable to diff situations, playful, doesn't bark, loves all people. There are many drawbacks to small breeds, most are very delicate and children should not be left alone with them, as the pup will be easily overwhelmed and unable to defend themself. But I believe ALL dogs should be supervised when with children, for both parties sake. Harley needs grooming, but he does not shed as he has hair instead of fur. He is also hypo-allergenic. I have asthma and allergies, and am allergic to dogs and cats, but not him. The breed lives a long time usually, and have little genetic health issues. He is a toy breed, which are notoriously hard to train. Adopting an older trained pup may be better for you, since you REALLY have to want a pup to train them, it's a lot of work. A LOT.
Check out the AKC website, and search by size. You can get alot of info there, and then do individual searches on those pups. Good luck in your decision =)