Everyone we talked to about our trip to London told us that the tower was the place to take kids, so this was at the top of our list of attractions to visit.
We arrived a little late in the afternoon, but were still able to join another group of tourists guided by a red and blue-clad "beefeater" through the grounds. This greatly enhanced our visit, as the wry-witted Yeoman Warder explained the history attached to the centuries-old buildings. The tour ended in the Chapel Royal of St. Peter ad Vincula, which covered the bones of hundreds of executed prisoners (including royalty) who did not visit the tower by choice.
Always a lover of Tudor history, I was especially fascinated by hearing about the "Queen's House" that was built for Anne Boleyn as a wedding present, only to hold her during the grim days that led up to her execution. The boys looked for the place in the stairs that once hid the bodies of two ill-fated princes who disappeared before their uncle took their throne. Then we took an hour or so to poke around the displays of royal armour in the White Tower, a building that was put up on orders of William the Conqueror!
While I've heard the queue to see the crown jewels can be long, we sped through near closing time. To top it all off, the kids spent a mint in the crowded gift shop when we were done with our visit. It was an enjoyable afternoon.
Entrance fees: £12 for adults, £10 for kids. Admission for kids under 5 is free.
Tip: After the tower, go down to the docks by the Tower Bridge and catch a boat ride on the Thames. This is a quick way to see a lot of the city with children.