whats worth doing in london with a 3yr & 4yr

[roastedfox]

going to london for the day next week and ds's have never been so want to get in as much as possible. am planning on taking them to see big ben and buckingham palace, any other ideas welcome please

forgot about the wheel! fantastic idea thanx
i remember going to the science museum when i was little and it was fab then!
thank you

I would avoid science museum and natural history museum on half term if you can...It gets so so busy!