London is a lot of walking! I vote for V&A or British Museum over Tate. Natural history great too.

Agree, no dungeon, they're too young.

Also I think they're too young for Sherlock Holmes - it's small and boring. My daughter loved it but she was 16 at the time I took her at her request and was watching Sherlock on netflix.

Harry Potter Studios is awesome and worth the trip, but perhaps when they are older? i'm thinking they may not even know Harry Potter yet? Madame Tussauds wax museum might actually have more characters they recognize - star wars, marvel, not sure.

I second Tower of London and Tower Bridge, just fabulous and a must see for all ages.

I also agree that St. Paul's cathedral an be enjoyable for all ages. It's big and pretty and has the whispering wall.

Not sure where you are staying but there are many many great parks throughout London. I also think St. James park is a nice choice and they sometimes have bands playing.

Covent Garden can be fun as someone mentioned. There is always lot of hustle and bustle there, street performers, etc. and pickpockets (that can be anywhere) but it can get crowded and you can easily be distracted with the street performers! So, keep smart under clothes wallets and hold hands in crowded areas!

Here's a day out of town thought: http://www.bekonscot.co.uk/

Went there when I was 4 and 7 (it's been around a while).

According to my next generation, between the Tate and the V&A the answer was always the National Gallery - or the National Portrait Gallery.

The crucial thing about Britain's major museums and art galleries is that they're all free. So no queues and no need to hang around any longer than a small child's attention span can handle. If they're clearly bored after 7 minutes, who cares? You just leave.

Why not go to two or three (especially around South Ken)? In an hour you can do taster sessions of the V&A, the Natural History Museum and the Science Museum.

A number of my 5-9 yo nieces and nephews LOVED the National and the NPG (next door to each other): a few minutes of their child-friendly tours gave them a hint of what galleries were like - and by quitting while we were all ahead, they never learned galleries were boring.

30 years later, they're either in those galleries' Friends' loyalty programmes. Or they keep telling me at clan gatherings how they learned a whole new side of life they'd never have stumbled over without those "wham, bam. thank you ma'am" sessions.

None of them - not even the nephew who became a Friends'Chair of one of the Tates - we ever dared drag to a Tate. Just not designed for younger people - though you do often see ambitious young mothers trying to inculcate their children. In our clan, Tates were one step too far.

Even there, though: both Tates are on glorious walks along the Thames kids (well, Flannerkids) will love. So it doesn't hurt to try. The Flannerclan, of course, doesn't hold with letting kids say they don't like things - till they've tried them

Wonderful! You guys are just amazing! Thank you so much for all of the suggestions and comments.
I often get asked: why take the kids? And then told: It will be fun!... but maybe not as fun!
Well... I recognize I may not be able to enjoy a few pubs or shows, or even some museums and tours, but I also believe that I can come back and do all of that when they are older and living their own lives with family. They are growing up So fast and I would love to instill some beautiful experiences in their lives while they are young. We went to Paris a couple of year ago, for a week, and at ages 2 and 4, they did wonderfully well, at the muse d'orsay, louvre, etc... as long as we rode carrousels, ferris wheels, we went to cirque d'hiver, etc. they loved it! They still talk about t and ask to go back!
So I surely appreciate all these comments. And I agree with you all that the Tate will be difficult for the kids. Perhaps we can take a stroll on the bridge and just walk over, even if just to see the building (in an architect and have always admired this Herzog and de Meuron's project).
Now this will be a stretch, but I'll give it is a shot: good Indian food and fish and chips around south Kensington or close to some of the places mentioned??
Thanks again!

Tulips.. yeah.. the fact is most little boys are not into princesses and queens and fancy jewels. Raised two and a girl.. and yeah, I bought my son a baby doll , I was going to be all gender neutral too.. But most kids just like what they like, and for most boys that doesn't include standing on a conveyor belt to see fancy jewels.. especially three year olds. I am surprised you think your 3 yr old son would enjoy it.. did he?

Following, as we're considering a trip with children of similar ages to yours. Please report back on how it went!

3 is very young - and my son enjoyed the tower just as much as his sisters did at that age. They all thought the ravens and the tour much more fun than the jewels, though.

Tate Modern; do the walk from Borough Market, and have a look inside. It's huge. They may have something striking, that the kids enjoy. Years ago there was a huge slide, from near the top to the ground floor, as part of an art installation. Now that, they enjoyed!

ooh, weren't the Slides GREAT! I wish they could be reprised some time