In Los Angeles, a 10 percent chance of rain in the forecast means it’s not going to rain. In London, a 10 percent chance of rain means it will rain 10 percent of the day.

At least that’s my conclusion after our recent week tourizing that fine city.

Each morning, we made sure to pack our rain jackets regardless of the forecast, and just about every day we used them. We had one truly rainy day, but were (as the Brits say) spoiled for choice about where to spend it, since London has so many great indoor options to entertain the kiddos: the British Museum, a science museum, a natural history museum and an aquarium, to name just a few.

Most of the major museums are free. Spending time in one of London’s many parks is also free, and renting a bike to tool around will cost you just two pounds for the day (about $3.50). We appreciated these wallet-friendly options, because otherwise London can be an expensive city. (Just one example: two loads of laundry at a laundrette near Marble Arch set me back over $30. The proprietor was lovely, though, and there are worse things than spending a morning chatting with fellow travelers from all over the world.)

Some things are definitely worth the expense. Among them:

The hop-on, hop-off buses. I’ve long been skeptical of the open-top buses that cruise big cities, but the Big Bus tour we took had a witty guide and offered a great overview of the city. Our tickets included a boat ride on the Thames and several free walking tours. You can get your tickets at most of the stops, or get them in advance for a discount online. (We spent about $130 for three people.)

The Harry Potter tour at the Warner Bros. studio. Visit the sets, check out the props, be blown away by the scale models used in making the film. The digital guides, with audio and video commentary, are worth getting. (With the guides, we spent about $200 for admission plus about $50 for rail tickets to get there.)

The Tower of London. A thousand years of history in one place, with lots to interest the kiddos. (Admission for three was about $70.)

Matilda. Yes, we could have seen this terrifically fun musical made from Roald Dahl’s book in New York, but I’m glad we waited to see it in its native habitat. If you book in advance, you can get a better deal than the nearly $300 I shelled out for two tickets…so do that.