There are various organizations that strongly advocate adopting dogs, rather than purchasing them. As volunteers with Great Dane rescue organizations we believe in and support adopting dogs. However that doesn't mean that purchasing a Great Dane from a responsible breeder is an incorrect decision for you and your family. Dogs from responsible breeders do NOT end up in shelters or rescues because the breeders support their puppy purchasers for the life of the puppy and will take back a puppy/adult dog if the puppy purchasers can't keep the dog.
On this page are resources that provide information on the topic.