Cavalier Spaniel, Cavalier Spaniel, Cavalier Spaniel.
These are absolutely fabulous family dogs, utterly loveable, hugely loving, full of spark and energy, but NOT in need of much by way of exercise (they can walk for miles, but ours don't get taken out for walks more than once or twice a week at most, and are totally healthy and happy on that).
They have a good bark (for security purposes), but are not yappy.
The only downside to this breed is some health issues, regarding heart probs, but go to a good breeder (I can recommend one if you ask).
We now have 2 Cavvies, a 10 year-old, and a loopy 4 year-old we adopted 2 years ago. Before that I had my first cavvy, who used to come to work with me.
They really are dogs which will fit into your lifestyle, rather than you having to radically alter how you live to accommodate the dog.
As you can tell, I'm smitten, and wouldn't suggest any other breed with small children