My family (myself, husband, 13yo son) have been to Vienna before during Christmastime. We have the opportunity to return in mid-March. While we would spend 4 days in Vienna again we have no idea where to spend the other days. We don't ski and are not winter sport enthusiasts. We have done the Wachau Valley already as well. I am sure we could spend 2 days in Salzburg but also looking for some other ideas. Any suggestions are appreciated!
If you're open to somewhere that isn't in Austria, I would say split your time between Vienna and Budapest.
Doesn't Rick have suggestions? Perhaps someplace like Graz, from where you can go to the farm where the Lippazaners grow up, or Linz.
I believe he recommends a day trip to Bratislava.
Not talking about day trips (e.g. Graz, Linz, Schneeberg, etc.), but Vienna has so much to offer (also for a teenager) besides the classic sights, that it is pretty easy to fill any number of days.
Have you been to Innsbruck? Mid March could still be skiing in the Alps. I see it's not on your list, but the train to Fulpmes from Innsbruck and the lift up for the experience and views (provided the lift is still running)? Innsbruck to Sterzing, Italy is not that far.
Not sure what if anything would be going on in/near Rust on Neusiedler See.
Zell am See, but the boats may not be running yet. Nearby is the Kitzsteinhorn 3029m top of Salzburg.
Way out I would say Lienz, but a long way and March is probably not the best time. Sunniest city in Austria.