Hamley's and The West End
Activity: Hamley's and The West End. Tube Stop: Oxford Circus. Cost: Free, unless you buy a toy! Hours: 10-9, closes 6 pm Sundays.
Time to treat the kids to a kid's activity! Go downtown to Piccadilly Circus and visit Hamley's! It's a fantastic and HUGE toy store. I may have spent hours in the Barbie section. While you're there and if your kids are old enough, book some tickets to see a show in The West End.
A word about British Theater. We Americans like movies. The Brits like live entertainment. In fact, seeing a movie will cost you more than seeing a play. It's considerably more acceptable to choose acting as a profession, probably because there is more of a market for it. Furthermore, this is my opinion, but stage acting is the higher art form than movie or TV acting. You don't get to have multiple cuts to get the right shot, you have to have everything memorized, you have to be able to enunciate and project and hold a crowd's attention, and you have to be able to do this night after night. You'll find big name celebrities starring in some of the shows around town. I would recommend seeing one big musical while you're here, one Shakespeare play, and one regular play in a smaller theater. They all show a different side of British theater.