Um, you should never get anotehr dog to solve one's boredness. That is solved by more interaction and exersice with its family. You may now have two bored dogs. That is unless your dad has his own otehr reasons for wanting another dog.
Anyhoo it is a common myth that two breeds wont get along, its rubbish and if you secure them with a great healthy start then everything should be fine.
The number one mistake people make is bringing the new puppy in the house to meet the resident dog. have your dad walk teh puppy down the street and have another adult walk the resident doggy to meet them on neutral territory so the resident dog dosnt get territorial.
Next Great Danes are very well mannered dogs so thats good news.
Also you need to help your resident dog show the lil one who is boss so there isnt a figth for who is the boss. The little puppy needs to know his place or he will challenge the big dog. If the big dog growls at the little one at first its ok, he is telling him this is my house you repsect it. As humans we tend to push the older dog away because "he should now better" but all that does it teach the puppy that its ok to cahllenge and that makes for mor eproblems. Dont let the puppy steal toys from the older dog, always feed the older dog first and give him priority or you'll have a war.
Lastly walk tehm together and encourage play, the dogs that play together stay together.
Good luck and we'd love to see pics when you get em!