London

We need to know what sort of sightseeing/experiences you prefer to answer this question. You could spend 3 weeks in London and not run out of things to do.

Rick lists his top sightseeing suggestions for many major cities on this website. You can find his London favorites here:

enter link description here -- click on At a Glance

In case you are not aware, many of London's best/largest museums are free. That includes the British Museum, but it is typically very crowded.

Been going to London since 1972. Never bored as it’s always changing, always the same.

What do you enjoy doing when you travel?

A bit difficult offering ideas when you haven’t shared what you like?

Theatre? Museums? Tourist traps? Street Markets? Art Galleries? Music? Foodie? WW2? Parks?

kathryn, I know you've traveled with some very large groups in the past. Are you doing that on this trip? Or is this a smaller group? As the others have pointed out, it would really be helpful if you would let us know how many people are going, the time of year you're going, the interests of the people that are going, and so on.

London really is a wonderful city, and I think you would really enjoy it, but to get the best out of it, more specifics would be helpful.

Thank you all for your replies! Yes, we are the same group, minus 4 travelers. So, this trip is a total of 7 adults and 3 young children.
We want to see the main tourist attractions and the children and parents are troopers, so will go at the same pace for the most part as the adults. :)

So, in order of must sees and what is near each other, what would be your top things/places to see/do in 3 days?
Thanks so much!

There is a 7-day itinerary here on the RS website - you could pick and choose the attractions and activities that appeal to you:

https://www.ricksteves.com/europe/england/london-itinerary

To maximize your short time in London, the RS London guidebook would be invaluable - or the Great Britain book if your visit includes other areas.

Some of our highlights the last trip:
British Museum (spent 2-3 hours and didn't see anywhere near everything)
Tower of London (took us 3-4 hours)
Afternoon tea
Westminster Abbey
Tower Bridge (Kids loved due to glass viewing panels)
Churchill War Rooms (husband #1 location, kids found it meh but didn't hate it)
Parks, we spent a lot of time walking parks and stopping at playgrounds

I generally don't plan more than 2 larger activities in a day, so you're looking at 6 max locations with a few walk by options so you'll have to narrow it down based on what your interests are as there are endless things to do in London. One day could be Tower of London followed by Tower Bridge. Another day British Museum followed by Westminster Abbey ending in a park. 3rd day Churchill War Rooms, afternoon tea, walking parks with a stroll past Buckingham Palace.

With your group, definitely Tower of London - and take your time here for the kids to absorb things. British Museum. For the kids I would go to the Science Museum out in South Kensington.

https://www.sciencemuseum.org.uk

I would not recommend the Churchill War Rooms with small children. The corridors down there are cramped and honestly they will be bored. IF the adults decide this is something they want to do, have a couple of people take the kids across the street to St James's Park to look at the ducks or something.

Did you get accommodations worked out for the Isle of Man event?

I know your time is limited and this is kind of niche but — if you have any penguin lovers among the kids or adults, or general animal enthusiasts, I can highly recommend the London Zoo, aka Zoological Society London (ZSL). The Penguin Beach exhibit is one of the best I’ve seen (I am a penguin fan). The design has some nice natural elements and you can get up close and personal. Great for little kids. The zoo is in the north end of The Regent’s Park which itself is worth a stroll for anyone needing a nature break.