The best small family dog is the Bichon Frise it's small and fit for family life. Take it from the owner of two Bichon Frise.
dachshund
a chiuaua
If you do not have a dog yet, wait till your kids are a bit bigger before you get one (I am not saying don't get a dog, dogs are great as part of a family but with very young kids there may be hygiene problems that are best avoided)
Jack Russells are small, smart, and high energy. Maybe a good pick for you.
A Basset Hound.
A beagle
It depends on what you like :)
English bull dog
The best way for a small dog to enter the house is through the doggie door.
A beagle
Border collie
a cockapoo