They may never go back to the park once they've seen the playgrounds of England's kings and queens. That's when you show them of the cells at Tower of London. It's all in a royal tour of London. Here are the easy highlights.
1. City of London and Southbank
Get up early and make your first stop The Tower of London. Queues are horrific, so it really should be the first thing you do. Afterwards, hop on a bus heading west and get off at the Millenium Bridge, right by St Paul's Cathedral. While you are there and if you're feeling up to it, climb the cathedral stairs to the top for the gorgeous views. (And remember: Exercise cures jetlag.)
Then you have two options:
a. Walk across Millenium Bridge and have lunch at the cafe at Tate Modern, followed by a quick look at the Turbine Hall. The museum is great for families, but with limited time, you should check whether the current shows and the permanent collection would be of interest.
b. Grab a quick lunch at the Tate Modern and walk over to Shakespeare's Globe Theatre for a tour and/or a show.
2. Royal London
Walk through Hyde Park, past the Serpentine and the Princess Diana Memorial, and into Green Park. Head towards Buckingham Palace for the Changing of the Guard, which usually takes place around 11 a.m., or visit Spencer House, the only 18th-century private palace left in London. Continue walking to Westminster Abbey, then across Westminster Bridge (it has great views of Big Ben and the Houses of Parliament) to London Eye. This is tricky: It seems like a silly, touristy idea, but on a clear day, the views are stunning. Pre-book fast-track tickets if you go.
3. Out-of-Town Palaces
If you want to leave London Proper, Windsor Castle is fantastic, an easy train ride from Paddington Station. The train drops you at the bottom of the hill, and the Castle hovers over everything in this pretty town. Get the audio guide for the kids; it's great. The trip may not even eat an entire day: You can get to Windsor by 9:30, visit the castle, have lunch, and be back 3 p.m., with plenty of time for a nap and dinner. Another easy option is Hampton Court Palace, which is also a quick train ride.