London-Paris-Munich?

If you want side trips, then I would suggest a week in London and a week in Paris, as you don’t really have time for a third country. There is enough in each city to fill more than a week even without day trips. Your first day or two are going to be lost to jet lag.

It depends on your interests - from London, you could head to York or Bath. From Paris, I would opt for Normandy or the Loire.

You might consider the Colmar area. Fly into London, spend 4-5 nights (minimum), train to Paris, and continue on to Colmar by train. Spend 3 nights, maybe including a day trip to Europa Park. Train back to Paris for 4-5 nights. Fly home from there.

Colmar (and surrounding villages) will give you a much different feel from being in the big cities.

Unless you already have places that you know you REALLY, REALLY, REALLY want to visit, I'd keep the number of location changes to a minimum. Especially with summer crowds.

Unless you've visited several times before, London and Paris could easily each fill a week. Look at the guidebooks to find either several day trips from each city, OR select one 2-3 day side trip to explore somewhere fairly close (time wise) to each city.

Keep in tind that your arrival day in London will be a jet lagged blur, each location change will result in the loss of 1/2 day sightseeing., and your final day will be shortened by your departure.

The Loire is not next-to Normandy. Munich is not the only interesting part of Germany. Do you want to rent a car, or want to avoid driving a car? Do you know about Multi- City (Open-Jaw) air tickets? Have you set foot in Europe before?

Have a look at our host's free travel tips, blue menu top left.

Edit: The first trip to Europe my wife and I took was a week in London followed by a week in Paris. We have returned to both those cities many times in the following 35 years, and have not exhausted their attractions. There's nothing wrong with the Normandy beaches, but unless you had close relatives who served there, you may be mistaken in prioritizing that for your first visit to France.

https://community.ricksteves.com/travel-forum/france/day-trip-from-paris-to-d-day-beaches-acf8ace3-7773-4e57-b464-b178dcd45e1f

I am inclined to suggest Amsterdam for a third city, because it (and its daytrips) also cannot be exhausted in a week. And its easy to fly home from. If you insist on Germany (why is that?), Berlin fits the same purpose. I happen to like Cologne, which is closer, but it's not a major city of the world.

You know that London and Paris are musts, and beyond that you don't know. With just two weeks, I'd stick with London and Paris. Bath could be a long day trip from London if you want, so could Stonehenge, or Windsor, Oxford, Cambridge, Hampton Court, Greenwich, Canterbury, and lots of other choices, but London has more than enough to keep you busy for a week. So does Paris, but possible day trips include Versailles, Chartres, Giverny, and others.

I wouldn't recommend Normandy as a day trip -- it takes so long to get there and back that you have very little time to see the D-Day sites or much else. If it's important enough, you could spend a night there (Bayeux is good).

Fly into one city and home from the other, taking the Eurostar train between them, so you don't spend time and money backtracking. Germany has many great places to visit, including Munich, but I suggest saving that for a future trip. Likewise the Loire.

Colmar is on my bucket list. I like the idea of London and Paris and Colmar. Depending on how many things you want to do in London, I would consider spending two or three(less expensive) nights somewhere easily reachable from London by train, such as York or Bath. You could see something in London in the AM and take a train to a less expensive city that afternoon. It would help us on the forum if you told us your interests and must sees. Are you willing to rent a car to go to the Loire Valley? I definitely would not add a third country(Germany).

I agree with the others about visiting no more than two countries and I also agree with Tom about choosing England or France this time around. If you do decide to visit both countries then consider staying in one location in each country and taking day trips. There is nothing fun about trying to get from one location to another.

Another vote for just England and France. Don’t think that you can just stay in London and Paris and make day trips from there, however. To properly see the countryside, stay in a smaller town outside London and get a car unless you can find decent bus tours. Driving a car isn’t that difficult, even on the ‘wrong’ side of the street.

You can probably get a good D-Day tour from the Bayeaux or other area town, but for the Loire you really need a car.

Where do your kids want to go? Having travelled with my son at 16 and 17 , we had a much better time when we were in the country he wanted to see (France) then in the one he didnt (Italy). make your kids active planners .
I tend to like at least 2 days in a quieter or smaller location after a big city . Bayeaux was a great overnight for us after Paris . Long train ride to a tour of Normandy beaches, overnight in Bayeaux with leisurely sightseeing in Bayeaux the next day and return on evening train.
We loved an overnight in York after 4 days in London and an overnight in Canterbury as well.