Pre-tour site-seeing - suggestions in Germany?

Dachau is a MUST SEE in my opinion. I don't see how you can be in Hitler territory and not see it.

We love bighattours.com for Dachau - he is an American, but has been living in Germany for many years.

We like Hotel Schlicker in Munich.

We love Nuremberg also - Hotel Victoria.

Frankfurt is not a fav of mine, but love Munich, Vienna, and Salzburg.

You may be late booking the hotels we love as you will be there Xmas Market season and the best hotels near the markets book out far in advance.

I would go to Rothenburg, either on the day you arrive ( if you arrive early ) or after a night in Frankfurt if your plane arrives in the afternoon.

I know firsthand that Christmas fairs in Germany are amazing. My favorite is the Christkindlmarkt at Marienplatz. It is one of the oldest in Germany, with a great atmosphere, but I didn't dare to try the roasted chestnuts)

My sister would like to see Dachau, but I am also thinking Rothenburg or Nuremberg. Considering the travel time (we will most likely be traveling by train) I want to make the most of these few extra days.

I would head from Frankfurt to Rothenburg ob der Tauber when you get in (or early the next morning, as stephen mentioned), spend possibly Saturday and definitely Sunday night there, which will give your sister and husband the opportunity to see the very charming and iconic village of Rothenburg.

After that, head to Munich early Monday morning, drop off your luggage at your hotel, then take the train to Dachau, which is only about 10-15 minutes by train, and visit the concentration camp. After that, head back to Munich so you can check in and have a nice evening before your tour. You do not need to book a tour for Dachau, imo. It is easily seen on your own.

Between Frankfurt and Rothenburg there is the city of Wurzburg and it's right on the way train wise. The Prince Bishop's Residenze is worth seeing -- especially the small chapel on one end. Google it and see what you think.

I highly recommend visiting a spa when you arrive. Especially for your working husband and sister, this will be a nice transition to vacation mode. Any town with Bad in its name should have a thermal spa. Even better will be to find one with a Xmas market that has opened by 11/23. Even if you just stay one night and then move on, you'll be glad you did. Especially when you move on to Munich (to, fingers-crossed, the same hotel you'll be staying in with RS tour) and take your sister out to Dachau. I wouldn't recommend trying to pack in anything else. I tried to find a spa town close to Munich so you could go there AFTER seeing Dachau, but I didn't find anything.

In Munich, the BMW museum is pretty cool if you like cars.

I think you would have to go a bit out of your way to find a spa town, and given that your husband and sister have never been to Germany, you could definitely find some place more iconic like Rothenburg, or Nuremberg, which is also a wonderful destination. I myself would have no desire to visit a spa town right after coming to Germany. Maybe if had a few weeks or more, but not in your time frame.

Mardee wants iconic Germany, not out of the way. How about Baden Baden? Direct trains from Frankfurt and to Munich. Christmas market will be open on the 21st of November.
I recently flew into Frankfurt from the US West Coast, and I very much enjoyed "recovering" in the thermal pool near my hotel in Wiesbaden, which I selected specifically for that purpose. I imagine I would like it even more in late November.

You fly in on a Saturday. The 24th is a Sunday and no matter where you go in Germany much will be closed. I suggest Nuremberg is the best option in this regard. If you stay in the Altstadt you will have a number of hotels and restaurants available and some services, like the bookstore, in the Bahnhof. Nuremberg is an easy city to walk around, and the German National Museum is open Sundays, https://www.gnm.de/, and so are the Train and Toy museums. I think you can also do the castle tour, but that may be seasonal.

That would allow you to continue to explore the city or choose another destination on Monday. Either way you want to be in Munich Monday night.

You could easily visit Ingolstadt, Augsburg, or Regensburg en route to Munich via the train. Ingolstadt is a stop on the RE1 which is direct into Munich. Augsburg and Regensburg are direct from Nuremberg and direct into Munich.

You could also go straight to Munich and then visit Dachau, but I don't recommend it.

just know the Xmas Market in BadenBaden is very UNDERwhelming compared to the ones in Regensburg, Nuremberg, Salzburg, etc. We've been twice and won't return.

Just know if you do Dachau on your own - there is a Train and a bus to get there. It is easy, but you will see and LEARN SO MUCH MORE with a guide - we've been twice and learned so much more with a guide than on our own.

Also - Rothenburg, while stunning, is NOT easy to get to and requires a few train changes. I think the Thurn & Taxis market in Regensburg is MUCH better than Rothenburg. And Nuremberg is also excellent and has the famous Kathe Wohlfahrt store like Rothenburg has. Just trying to keep things simpler. Regensburg was not damaged in WW2, so all original. The town is amazing and deserves a couple days. The Cathedral is great, the main market at the cathedral is good, but the private Thurn & Taxis is one of the best in all of Europe. I don't necessarily think the Palace is worth touring - but the market is a DO NOT MISS. The bridge area is fabulous and Regensburg is the home to the oldest sausage shop in Europe.

While we like the 3 markets in Munich near Marienplatz - we much prefer Regensburg, Nuremberg, Salzburg, Vienna, Passau for the atmosphere and products and food.

Can you change your ticket and fly into Munich instead?

China- The OP is on tour starting NOV 26th. The only market, of those you mention, that will be open before that date is Regensburg.

We just got back from this same RS tour. We did 4 days prior to start in Munich and it was well worth it. Plenty to do. We went to the "Disney" castle ----- Went on a bus tour with Radius tours. We also did a 3rd Reich walking with Radius --- so interesting. After the walking tour we went back to do the 4 floors of the Nazi Documentation Museum ---- FREE --- well worth a rainy afternoon visit. We did a tour of the Residenz palace. The only hard part was finding the entrance. It was Oktoberfest too so we spent an afternoon (our first RS tour day) at Octoberfest. Munich is very walkable. We wanted to go to Dachau but just didn't have the time.

If you are flying into Frankfurt on 23 Nov. suggest staying overnight in Frankfurt and do some sightseeing there. There are plenty of historic sites to see and you can get a good nights sleep after your long flight. The next day, you could go to the Rüdesheim Christmas market, which is one of the few markets that is open on Toten Sonntag. They have a "silent" market, which means the carousels, etc. do not play music. I went last year and really liked not hearing the same songs all day, while walking around.
Heading south the next day, Heidelberg and Worms will have their markets open, and both are worth doing some sightseeing in.