If you want a dog to show, you need to buy from a person who shows their dogs successfully. Someone who just says they have "show lines" may or may not have a dog that meets the breed standard. However, even top show breeders will have pet quality puppies, so you need to find a breeder you can trust and that can mentor you if you want to get into showing. A top quality show puppy will be a little harder to find, so you will need to find a breeder that is willing to work with "newbies" to showing. Most of the time you can expect to have a contract with a co-ownership and other "strings" on a potential show puppy. Your puppy, should at the very least, be champion sired. (Just having champions in it's background is not enough).
I'd suggest starting with the Yorkshire Terrier Club of America and then find a member club in your state/city. You can get breeder referrals from them and start learning more about showing. I'd suggest you go to as many dog shows as possible and start talking to the Yorkie people there. You will learn alot and you will see different 'types' of dogs and then you can decide which breeder's dogs appeal to you.
You can also contact your local all-breed kennel club and start getting involved there. They will have conformation training classes that you will want to start in on once your puppy is about 4 months old so you can start training in ring etiquette. There will be "fun matches" available that you can practice on, etc. Obviously Yorkies that are being shown have meticulous coat care, including putting them in oil, so you will NEED a breeder/mentor that will show you the ropes.
Oh, and to answer your original question.... those puppies sure don't look like purebred Yorkies to me.
