Traveling 14 days or Less in Germany, Switzerland and Belgium

Brussels is worth one day, but nearby Brugges is a definite must see.

You will be traveling the entire length of Germany, that is a long drive. With more than two in your party, I would think renting a car would be cheaper than the trains. Frankly, you would be better off visiting some North German places, as well as Denmark and perhaps Stockholm.

If you go to Switzerland, also consider Interlakken.

On your way from Kiel to Switzerland, you may wish to go a bit west and hit the Rhine Valley, starting with Cologne. Rudesheim is nice and you could take a short cruise on the Rhine. Heidelberg is nice, then down to Strasbourg, France and/or Triberg and the Black Forest.

If you have time after Switzerland, you could take in Luxembourg in route to Brussels. Trier, Germany is very historic as well.

How many places do you want to visit in Germany, and why do you want to finish in Brussels? I hope there is more that you want to do in Switzerland besides this one brief canyon hike, to justify the time it would take to get there.

I highly suggest you figure out exactly what places you want to visit, and what you want to do in each place. Doing this, plus adding travel times between each place, will give you a good idea of just how many days you would need. Then you can edit to fit your time constraints.

Most Americans seem to jump on rental cars as their first transportation option. But in Europe, it is often the LAST thing they should do. Gas is expensive. Parking in large towns and cities is difficult and expensive. You will need an International Drivers Permit for each licensed driver. If you drop the car in a different country than you picked up from, the drop off fees can be many hundreds of Euros. You would need to buy a vignette to drive in Switzerland. And you would have to familiarize yourself with European road signage and driving laws. Travelling by train (provided you haven't made the newbie mistake of packing huge suitcases) is frequently the easier, cheaper, and often faster choice. Especially if most of your stays will be in cities. Cars are great if you are going to be in a rural area poorly serviced by public transportation. You might get by with just renting for a day or 2.

If you aren't familiar with European trains, read up on this site ( it really should be required reading for travel in Europe): https://www.seat61.com/

Of course you CAN do that. But perhaps there are other options that would make better sense both in terms of time and money for a way to spend 2 weeks starting in Kiel, Germany.

Do you know how far that is? Have you google mapped it? Google says about 20 driving hours from Kiel to Interlaken to Brussels. That might not sound like a lot over 14 days but the post above just told you some (not even all) the drawbacks of driving in Europe and most people say to add at least half again to what google maps says. And that's all highway driving skipping probably literally hundreds of worthwhile places. If you had two months instead of two weeks I'd say you could make a really nice trip of it.

You ask for thoughts. I personally wouldn't do it. If you want to spend an extra two weeks I'd look at either going to Switzerland - and fly home from there (Zurich) OR go to Belgium. Look at some maps - both train and driving maps - and see if there aren't some places closer to where you are starting from. Of course you could always fly from Germany to anywhere you like in Europe. Two weeks is as long as most have for their whole vacation.

I like CJean's answer. You haven't named a single spot in Germany that you want to see. Whether you should have a car is intimately involved in that tentative list. Note how far Kiel is from big cities. Will you sleep in Berlin the night before, or Hamburg, or where? Would you add nights there? (A week is not too long for a first visit to Berlin.)

I haven't seen the Gletscherschlucht, but most parents posting here are unwilling to go against a request from a child. But it is way out of the way for your OP objectives. How many people on this trip have been to Europe before? Where? You are treating Germany, Switzerland, and Belgium as if they are like visiting Boston and being sure to see Salem and Rhode Island. It's not like that.

What are the usual interests of the children and you? Modern art? Old art? Architecture? World Wars? Hiking and camping? Roman remains? Medieval life? Food? Beer? Wine? Science and aerospace? Waterfalls and rivers? Good internet for their cellphones?

Renting a car is not a good idea.
It is a very long drive from the Baltic coast (Kiel) to Switzerland.
Renting a car in one country and returning it in another one is very expensive.
And a car is useless in a city.

And I too am not sure why you want to end in Brussels. Better places in Belgium (Brugge, Ghent), and it involves doubling back north.
You say 10 days. I would then say 3 locations 3 + 3 + 3 nights, or maximum 4 locations (3 + 2 + 2 + 3)

You could do Kiel --> Belgium (if you insist) --> Paris --> Switzerland --> fly out of Zürich
Or: Kiel --> Location 1 in Germany --> Location 2 in Germany --> Switzerland --> fly out of Zürich

My thought: Kiel --> Berlin (3 nights) --> Prague (2 nights) --> Munich (2 nights) --> Grindelwald (3 nights) --> fly out of Zürich
All by train.

If you don't know where to find train info, start with the "Man in Seat 61" website.
Start with this beginners' guide: https://www.seat61.com/Europe-train-travel.htm
He the has pages for each route, describing the service, and where to find times and buy tickets.