I've been to London, and if you want to go inside all of these attractions then, good luck. There are several tour buses (double deckers!!) that go around London and you could probably see most or all of these landmarks. The cool thing about the tour buses is that it makes stops, and you can get off, look around, wait for the next one, and get back on. If you want to do the tour bus thing, I would ask somebody at the hotel you will be staying at (that is what my family did). The changing of the guard is cool, but it drags on and on (just thought I'd forewarn you).