Two weeks in the fall.

"Including the Rhine in Cologne days because I'm not sure where we'd store our bags while doing a short cruise or going into some of those cities unless we have a car... Any suggestions?"

The Rhine is more than just a cruise... You can also tour the castles and villages there if you stay overnight. Marksburg Castle in Braubach and Rheinfels in St. Goar are great tour options. Boppard, St. Goar, Oberwesel, and Bacharach, all on the left bank of the Rhine south of Koblenz, are good towns to visit and to stay in. So is Braubach on the right bank, just south of Koblenz. A car is not needed. Trains run along both left and right river banks. Here's a train line map for Cologne-Bingen on the left bank. And this map shows the train line on the opposite side of the river where Braubach is located.

September is prime time for weekend wine fests in the Rhine towns. These are much more local-color events than Oktoberfest. What weekends will you be in Germany?

Thanks! We're thinking the Rhine hour cruise, and a few sites, as a day trip because we don't want to cram it in on our way from Cologne to Munich. We also don't want to stay overnight in more cities.

"We also don't want to stay overnight in more cities. "

OK... moving to a new place means checking out, toting your bags, and checking in again somewhere else. For this reason, I like day trips too and I always plan them into my trips. But not all day trip destinations are equally easy - a lengthy day trip like this one also has its drawbacks; here are a couple of considerations.

• You'll spend 3.5 - 6 hours on trains to reach the scenic part of the Rhine - and to return the same way you came through the same scenery (which isn't all that scenic, actually.) Then you still have to travel to Munich.
• You may be missing out on a special experience. All your German cities are post-war-rebuilt places that were rubble just 70 years ago. Cologne, 1945. It just might add to your cultural experience to spend 1 or more nights in a scenic old-world village, not in a generic big-city hotel, but maybe in a castle (there are several Rhine castle-hotels that have been around for centuries,) a winery/B&B like this one in Boppard, or an old-world half-timbered building like this historic inn built in 1552 in Oberwesel, operated for 6 generations by the same family. If you stay in places like these, you'll escape all those big cities for a brief while.
• You might not need to move at all. You could easily leave Amsterdam in the morning, arrive in the scenic part of the Rhine in the evening, and in between make a stopover of 5+ hours to see the sights that interest you in Cologne. Spend all 3 nights and 2 full days in the Middle Rhine Valley instead.
• Fitting all the interesting and fun things in the Middle Rhine Valley into a day trip from Cologne is impossible.

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Russ, I've been doing more research on the area and agree with you. Years ago we stayed in Ingolstadt for a few days on business and enjoyed it a lot. This time, Berlin was added more out of obligation than desire. Maybe it is better to skip it on this trip and reallocate those days between the Rhine valley and Vienna. Cologne is where friends live.

I don't understand why you would fly into Schiphol to go to Cologne. Frankfurt and Düsseldorf are both major international airports that are less than an hour from Cologne by train.

There are direct flights from where we live to Schiphol and Munich. They save us a minimum of four hours over one-stop flights.

"There are direct flights from where we live to Schiphol and Munich. They save us a minimum of four hours over one-stop flights. "

Yes, but it costs both time and money to get from either Schiphol or Munich airports to Cologne. And prebooking a train to connect with a flight arriving from the US is risky, so you may need to buy a last minute train ticket (potentially expensive). There's also the fact that if you take a connecting flight, the airline handles your bags to the final airport; if you take a flight to a train, YOU have to do all the handling.

I'm not saying you shouldn't take the nonstop flight, but be sure you figure all the factors before making a decision.

If you are changing planes, you can not only fly to Frankfurt or Düsseldorf, but also to Cologne itself. The airport is called Cologne-Bonn, code CGN, and is between those two cities.