Almost any dog will be loyal; being loyal to their pack is part of being a dog. Not all breeds get along well with children; usually the larger breeds do well with small children because they aren't so delicate and can better handle the rough and tumble of young children. I've seen lots of breeds be wonderful pets in families with young children: Boxers, German Shepherds, Great Danes, Golden Retrievers, Labrador Retrievers. Get a book from your local public library and do a little reading about different breeds; some require frequent grooming, some need a lot of exercise, etc. and you'd be wise to pick a dog that will be good match for your family's lifestyle. Then go to your local animal shelter; there will almost certainly be a puppy or young dog there that would be perfect for you.
It depends on the size dog you want to get. Golden Retrievers and Labrador Retrievers are some of the nicest dogs you will ever meet. I've had several of them myself and they are wonderful animals. They are also good with children. Make sure you are really serious about getting a dog though because they need people to love and care for them. Petfinder.com is a great way to rescue dogs and cats from all over the country. Good luck!