Since Germany is my home country and I have to travel around on a weekly basis I may offer a few hints:
It depends on the routes:
- There are some very good high-speed lines which offer a very good service - there the train is much easier than a plane.
These are for example: Cologne-Frankfurt-Stuttgart or Hamburg-Berlin or Hannover-Frankfurt.
- There are some connections that are very bad (train lines like 150 years ago, old coughpy and dirty trains).
Worst Examples: Munich-Prague, Nuernberg-Dresden.
So in General North-South is easy East-West is a bit of a problem.
Do not expect to have WiFi on board. That is a national disgrace.
Have a look at long distance bus services that are offering dirty cheap rides between major towns (and working wifi on board).
www.flixbus.de is the place to look as Flixbus is now the monopoly operator.
General Rules:
Try to get on direct trains. German Railways is known for their disruptions and delays. So you may have a good chance of losing your connection.
I had a 2,5 hour delay on a train ride form Frankfurt to Düsseldorf caused by an incident on the high-speed-line.
We did take the scenic Rhine tour on the old tracks, which was amazing but very slow.
Tickets:
- Have a look at the Rail passes or Saver Tickets.
- Saver Tickets are only for special trains, but are very cheap if you book early.
- Have a look at first class tickets. They come with seat reservations and have lounge access in a few train stations (free toilet, coffee, soft drinks,...)
Traveling with a kid:
- I preferred flying, as it is easier to keep the kid quiet for 1h flying than for a few hours in the train, but again it depends on the routes.
If you want to see what is in between: Take the train as a scenic ride: Especially Frankfurt-Mainz-Cologne is beautiful on the Rhine river.
Your routes:
London-Cologne:
If you want to visit Brussels in between take the train.
Otherwise: Fly!
Cologne-Berlin:
Flying is easier and quicker, train connection not so good. I would prefer flying.
If you try Air Berlin (to earn a few QF SCs and points) be aware that they are in a not so good financial condition. They should be safe for the next 12 months, but nobody knows what will happen soon.
Cologne Airport has a good train connection and Berlin TXL Airport is quite close to the town.
Cologne: The Cathedral is a must, then go to some pubs. Cologne people are very open minded and friendly, you will find friends in the pup within minutes!
Berlin-Prague:
Train may be an option. You may stop in Dresden, which has been rebuilt after 1990 and is very nice for a stopover.
The Elbe River has very scenic points (You may like Bad Schandau and stroll around there if you like a bit of nature).
Prague-Munich:
Trains are a disgrace, very slow. But the ride is scenic as well. You may prefer the long-distance bus.
Stopover: You may stop in Regensburg (the place where I live). UNESCO World Heritage. 2000 years old, town form 14th century, saved in WWII.
Nice place to stay a day or two. Must see: Cathedral and historic (Stone) bridge over the Danube river.
Regensburg-Munich can be done by train.
Munich (my home town): Lots of things to do:
Go to the Hofbräuhaus to take a photo, but drink you beer elsewhere (tourist trap).
In summer with a kid: Stop at one of the lakes in the south (Tegernsee in the mountains, Starnberger See is very close to munich,...)
There are boat rides and you can stop for a swim.
Munich-Zurich:
Same as MUC-PRG: A route that looks close, but can be a pain to travel (part of my weekly commuting routine).
Train: Takes very long. Flying: Very expensive due LH Monopoly and long travel times to MUC airport.
Maybe Bus.
If I were you: I would hire a car in Munich and drive a scenic way. Neuschwanstein is basically on the way to Zurich.
I would slowly do a nice day trip on that way and book a one way car.
My suggestions in Stops:
Kloster Andechs : Great Beer Garden and Church
Then: One of the Lakes: Starnberger See:
Maybe:
https://www.buchheimmuseum.de which is nice.
Then: Ettal and Linderhof Castler (which is worth to visit inside), as Ludwig II has finished it.
www.schlosslinderhof.de/
Then:
Pilgrimage Church of the Scourged Saviour
UNESCO World Heritage Nice (just a short stopover)
Then: Neuschwanstein
If you run out of time, do not visit it form the inside, as Ludwig II did die before finishing it. Inside is not impressive!
www.neuschwanstein.de/
Take a walk to the little bridge behind the castle and make a photo.
In summer, bring your bathers as there is a nice little lake there.
Then: Head on to Lindau:
Lake of constance, which is beautiful in the summer (may stop over there for a night).
Lots of things to do.
If the weather is nice take the cable car up the Pfänder in Bregenz (Austria).
The Pfänder - local mountain on Lake Constance
Short way: South of the lake!
Long scenic way: North of the lake and take the Ferry Meersburg-Konstanz.
Stop over in Konstanz.
You can get rid of your car in Konstanz (at the train station) and take the train to Zürich (which is fast and convenient).
This will save you the toll sticker for Switzerland and the international surcharge.
Be aware that the road north of the lake of constance is very congested. Beautiful, but very slow.
Toll roads: No toll in Germany, but you need to buy Toll Stickers for Austria and Switzerland in advance (at most fuel stations near the border).
Possible drop off points for the car (in Germany):
Lindau: Train to ZRH.
Friedrichshafen: Ferry + Train to ZRH (very scenic way). FDH has a nice shore, but is ugly (again WWII).
Car Ferry to Konstanz + Train to ZRH (1-1.5h scenic car ride).