Children's zoo at battersea park Love the aquarium If you go to the natural history museum and its a hot day go to the fountains at the v&a for paddling after Duck tours are quite fun Museum of childhood Bethnal green The horniman museum is also supposed to be great.
Could you take the older boy to a show? DS1 is desperate to see a few things after West End Live at the weekend.
Diana Playground goes down very well with my boys (6 and 8). They also loved HMS Belfast and the Cutty Sark. Transport Museum is good and the Wallace Collection (lots of suits of armour). I hate it, but they enjoy seeing some of the performers in Covent Garden. You could also do a quick trip into the National Gallery (they liked seeing pictures they had talked about at school, but needs to be limited in time!!)
We're off to London for a week in August, I'll have DS1 (then 7) and DS2 (18m). What's great for them both to enjoy? Was thinking of the science museum, London Eye and the LT museum, but I cannot remember what's great since I moved out of London nearly 10 years away.
We will be able to get to Liverpool Street, Stratford and om the Victoria line and will be happy to travel all across London (the more the better for my train mad boys!).