9 day trip: London, Belgium, Amsterdam

Since I assume you’ll be jet lagged in London, add it there.

It isn’t clear in your post where you are flying home from. Regardless, I suggest you spend your last day within striking distance of the airport you are flying home from. If London, it is best to stay in London. With strike actions and delays possible, it is best to ensure you are a taxi ride away from your departure airport just in case.

I would definitely spend it in London! So many things to do / see!!!

You don't have "7 days to sightsee," you really have 5, plus 2 to get from London to Bruges and from Bruges to Amsterdam (not far). That's if your flights are "open jaw," into London and home from Amsterdam. If you have roundtrip flights to and from London, then you need another day (Friday) to get back there, and you're down to 4 days for just sightseeing.

If you're flying open jaw, then I'd spend the "extra day" in London, at the start of your trip, where you can get over jetlag and experience more of this huge city. Hopefully after this rapid trip you'll be able to return to at least some of these cities, whichever appeal to you most, for the time they deserve.

It's not going to take a full day to Bruges- that is a half day journey, so you'll have a full half day there on the Monday. Then do Ghent as a day from Bruges and stay there on Tuesday night.
Likewise Wednesday is a half day transfer, not a full day to Amsterdam. So you still have a good half day there on Wednesday..
If flying home from AMS you hopefully have a bit of time there on Saturday before flight time.
So in that case add the extra day to London.

Please excuse me for saying so, but you seem to think you can zap yourself from place to place in a second. Unless you can actually do that, you need to calculate time to get from A to B.
For instance, if your flight lands at 11 am, it can very easily take 2 hours before you arrive at your hotel in London.
The same for your Monday when you plan to train from London to Bruges. This journey takes 3.5 hours, but you will lose another hour because of the time difference. So if you take the train in London at 9am, you will arrive in Bruges at around 1:30 pm. You’ll need at least another 30 minutes to reach your hotel, check in etc, which leaves very little time left to sight see Bruges.

You need to update your itinerary to include the time it takes to get from A to B. Then you have a more realistic idea of how much time you actually have to sight see.

After reading the replies, looks like it might be too jam packed! Providing a bit more context, we are flying in an out of London and I was going to risk taking a flight back Friday night or Saturday morning from Amsterdam. Now i'm leaning towards creating a different trip with max 3 days in London. How would you spend the rest of your days abroad?

Saturday - Half Day London

Sunday - London

Monday - Travel to New place / Half day in New place

Tuesday - Open

Wednesday - Open

Thursday - Open

Friday - Half day in new place/Travel back to London

Saturday - Flight Home

Is your new plan keeping you in England? With such a short trip that’s advisable. If so I would consider going directly to Bath from the airport, saving London for the end of the trip. If you spend 3 nights in Bath you could spend a day in Bath and the other day taking a Mad Max tour https://www.madmaxtours.co.uk/ to explore outside of Bath. I took one a couple of years ago and enjoyed it very much. I would then take the train to London spend the remaining nights there. It’s helpful to plan by how many nights you are spending somewhere to see how many full days you have. If you only have 6 nights I personally would spend them all in London. You could take a day trip to Bath from there if you really want to see it, or a day trip somewhere else.

Edited to add that to spend 3 days in London you will need to spend 4 nights there.

Note that Eurostar absolutely REQUIRES 90 minutes extra BEFORE boarding either way for UK immigration. Be sure to check their website the day before to see if it's even more in peak summer months. Round trip air to London is not always an actual bargain. Can you fly home from Amsterdam?

Eurostar is priced like an air ticket, with decreasing discounts as departure date approaches. But some non-business hour trains can still be cheaper. There's nothing scary about changing between trains, but I think each of your train trips will have at least one change, rolling your luggage.

You mentioned your husband has never been to London, so it is curious to limit time there to "max 3 days." It would be easy to spend a week in London and see things you've never seen. I personally would focus on London and some day trips and not try to add another country. If you must go somewhere else I'd pick either Bruges or Amsterdam but not both.

It would be helpful to know specifically when you are traveling. Summer months are crowded and you need to book things like Eurostar and hotels way ahead. This summer will be extra busy because of the Olympics and an anticipated heavy tourist season. I absolutely would not fly or train from Amsterdam to London on same the day your London flight departs, way too risky with potential delays. Depending on what airport and what time your flight leaves, you might consider staying the night near the airport.

“ How would you spend the rest of your days abroad?”

It’s not relevant how any of us here would spend the rest of our days abroad, what matters if how you want to spend them. We don’t know you and you’ve given us very little information about yourself, what your interests are etc etc.
It also seems you have already booked your plane tickets, is that correct? Or can you change them to fly home from another country? And when exactly will you be traveling? You could for instance combine London with Paris, but I wouldn’t do that during the Olympics.