I would recommend a Dachshund. Besides their loyalty and high intelligence, they have a mischievious quality unlike any other breed. A short-haired dachshund is hypoallergenic, and they range in size from under 10 pounds to about 30 pounds. For small children, I would recommend the latter. One caveat: Dachshunds are fiercely loyal to their owner. When they decide who that is, there is no changing their mind. They are social animals, who love attention, and will do practically anything to be the center of attention. However, like Britney, Paris, etc. they don't realize the difference between getting attention because they did something good or bad. Attention is attention to them. Another problem is that, like a cat, they have more curiosity than is healthy; dachshunds seldom live long enough to die of old age. As the owner of several dachshunds over the years, I have found that accidental deaths are common to the species. Such things as climbing up a ladder to the roof and jumping off, tackling a Doberman while at the vet's office because one decided to tear a tennis ball apart and eat the rubber center, digging under the fence and walking to the highway to play in traffic, tackling a rattlesnake, attacking a badger, etc. mean that they generate large numbers of vet bills and short lives.
Another excellent choice would be a Boston Terrier. Another smart, mischievious breed that is excellent with children. They are highly social, and would think that everyone who comes to visit is there just to visit them. They live for attention, and will really ham it when they think anybody will notice.
I wouldn't recommend a chihuahua. They are excellent for a private home without children, but they are really frail and delicate, and they have a tendency to have an attitude, and sometimes want to fight much larger dogs, be overly protective of their owners, and bite people who they think are a threat to said owner, all of which seems strange when you consider the fact that they are the size of a large mouse.