Definitely recommend Vienna Musical, Melk Abbey, and Rothenburg.
We went to Vienna Musical on a Christmas cruise. The performance was in a beautiful concert hall and included instrumental, vocal and dance performances. Lovely evening.
Melk Abbey is a must see and you will probably still have time to stroll through the town if you like.
Rothenburg is a delightful full day trip. Beautiful town and if you prefer there is a town square where you can sit and people watch. That's what my husband did. It's a great town to explore. We were there in November so we did Christmas shopping
We took the Baroque and Bavaria tour. I think it is pricey for what it is. We did have a very interesting local guide. After the tour we had pretzels and beer at the onsite brewery. Both were very good. Actually the beer is quite strong and they give you a huge glass. Most of our group had eaten and left for the gift shop, but my daughter and I were lingering over our beer since I was really feeling the effects. Our waiter asked if we were OK and I indicated that I was feeling the effects of the beer. He said he had something just for that. He brought us each a shot of liqueur! It was fantastic! Of course we had a great laugh and we each bought a bottle of the liqueur. So even though I think the trip was pricey, you never know when you are going to have one of those moments on a trip when you connect with someone and you have a fond memory that lasts.