To really make the most of London with your 7 year old in mind its a must to avoid official tours who love to hear their own voice. A trip to London dungeons is a must as its packed with history to improve their knowledge but delivered in a way so involving and exciting they wont realise they are learning. Great interation with staff and not to be missed. Lived here my whole life and its one of the many sites i could never be dissapointed with.
of course a 7 year old would appreciate england, you can do the educational yet fun things... such as hampton court palace...learn about kings and queens, got a huge maze there, loadsa fun for adults and kids :D then we have the london eye... cant come here without going on that! its so beautiful and you dont even realise your moving! you can see the whole of london...best bet to go at night when london is lit up, but the best thing is...there are tons of shops for mum ;)