Where to stay one night on the Rhine?

I have always stayed in Bacharach, but St. Goar and Oberwesel look interesting also.

We stayed in Boppard, partially due to hotel availability and in part because it's bigger than some of the other towns. We liked having a large choice of places to wander through, decent grocery stores, and a selection of bakeries.

We enjoyed Marksburg castle.

If you like the idea of staying in an 800 yr old castle, try Burg Stahleck in Bacharach. It's a youth hostel and it is very popular.
You definitely need reservations. You'll get to meet travellers from all over the world and the view from the terrace is fantastic! https://www.hihostels.com/hostels/bacharach

"Thus far our itinerary is to arrive Cologne the morning of the 24th...Then see the valley on the 25th..." Marksburg Castle, Rüdesheim and most of the other handsome Rhine Valley towns lie south of Koblenz, a healthy distance from Cologne, and it will take you most of the day on the 25th to do your exploring. Your plans for Cologne sound brief. So maybe you get an early start on the Rhine Valley and leave Cologne in the pm on 11/24...

The Middle Rhine Valley towns generally will be in varying states of hibernation. St. Goar will be deadsville (there are lots of empty storefronts there anyway these days.) Larger and more desirable is Boppard, but even there don't expect much to do in the evening. The one town that should be very peppy is Rüdesheim - it has a very attractive and popular Christmas market that opens 11/24. But you don't necessarily want to stay there on the 24th as R'heim is at the southern end of the valley and you'd be backtracking on 11/25 for your sightseeing - and rooms may be at a premium there. For overnight, I would probably opt for Braubach (home of Marksburg) or Boppard, both very nice places.

Marksburg Castle is stunning and offers the best castle tour in the Middle Rhine Valley no matter the time of year - and in late November, it may be the only place to get inside one for a look around.

Even if it were dark on the drive from Cologne, you wouldn't miss out on much scenery, the best of which is from Braubach south. The last tour of Marksburg castle is at 4 pm, so either you take your tour there Mon. afternoon (which would free up time on Tuesday for sure) or the next morning (opens 11:00.) Braubach is quite small but has a very fetching old town quarter and several places for an evening meal. The Gold Key (zum Goldenen Schlüssel) Inn will be closed but there are other room options in the cozy old town area like Gästehaus Wieghardt and other eateries as well, including Italian and German options.

Braubach accommodations

If you choose Boppard instead for your overnight spot, then you have choices to make...
a.) Drive from Cologne straight to Boppard on Monday for the night, then drive to Braubach Tue am for the castle tour (opens 11:00) OR...

b.) Do Marksburg Castle first on Monday by 4 pm, then drive over to Boppard for the night.

A car ferry operates between Filsen (just south of Braubach) and Boppard between 9 am and 18:00. There are other ferries to the south as well if you wish to cross the river elsewhere (no bridges between Koblenz and Mainz.)

On Tue, I would definitely find a way to fit in a visit to Rüdesheim's Christmas market (R'heim is south of Braubach on the east bank) and to see Bacharach and Oberwesel (just a few minutes apart, south of Boppard on the west bank) before the lengthy drive to Heidelberg.

Kevin,

I also like Bacharach, although I'm not sure how lively it will be in late November. As I recall, there is vehicle parking just outside the old walls. Any of the hotels will be able to provide specific information on parking.

My personal favorite is Burgh Stahleck in Bacharach. The town is a nice visit and the castle is one of the best hostels I've ever stayed in. Clean, well run. It will give the girls new experiences to check off the list: stay in a castle, stay in a hostel. Be sure to get reservations, they are always full - mostly with German families and groups.

I enjoy Rheinfels ruins in St. Goar. You can go where you like (including the landmine tunnels underground) and explore at will. On a foggy morning, you are likely to feel like you have the place to yourself. If you did Rheinfels and Marksburg, you would see the best in the area. I also like the one hour KD line boat ride from Bacharach to St. Goar. Use a family/group train pass to get on/off all day for cheap. Put those activities all together and you have a really full day.

There is another hostel in St. Goar. It's a decent enough hostel and doesn't need reservations. One caveat there is the bathrooms are communal. Showers and toilets are private but there's a unisex area for sinks. I went to take a shower one morning and it was packed with college age girls in towels. I thought I had accidentally gone in the wrong bathroom until they said (in German) that there was one shower available - then some white haired woman (probably an American tourist) kept trying to peak through the slit in the shower curtain.

"There is another hostel in St. Goar. It's a decent enough hostel and doesn't need reservations. One caveat there is the bathrooms are communal..."

This wonderful old villa used to be busy with bicyclists and independent hikers and travelers but is now undergoing extensive "modernization" - has been for a year or so - and it's likely to remain closed until Fall 2016. The hostel association, local governments, and the town of St. Goar are spending over $5 million on the place. The town's general demise of late (numerous closed storefronts) is no doubt connected to the closure - the hostel was a major draw. I guess it wasn't in compliance with the modern fire code and wasn't attracting the numbers it needed in its former state, so it will soon be all new and shiny and all about en-suite rooms for four like the other newly-remodeled hostels in Germany, but I will very much miss the handsome old place it once was.