Weather permitting, you'll be cruising Prince Christian Sound in Greenland - it's an awesome sight. Something that those of us who cruised this itinerary on Maasdam in 2000 will never forget.
The Grand Circle tour in Iceland is a must, IMHO - Geysir, Gullfoss and Thingvellir.
Qaqortoq is quaint - there is a series of stone sculptures in the town that you can easily walk around to view...and you can obtain descriptive sheets so you'll know what you're viewing.
It's a fantastic itinerary! Enjoy! I loved Iceland and Prince Christian Sound.