German Shepherds are great with kids, they even tend to protect their children when needed..
Labs are good, can be a lil hyperactive, but with training they make great dogs. Goldens are great.
With lil kids I would tend to stear (sp?) clear of many of the smaller breeds. Many of them tend not to be as friendly towards children.. But not all.. I would definately look into the different breeds and read about their temperments.
Also the humane society is a good place to go, take your kids see how the dogs interact with them, and who knows you may find your perfect companion there.. And if you do you can also be happy knowing you possibly kept an animal from being Euthanized..