I know it's not in the area, but the London Aquarium is always a winner with our boys! Infact I think they may even prefer the train ride up to Waterloo!!
I'll also be making sure I visit some of the local play cafes (I have a newborn and 2 very active boys!!) - Teeney Weenies in Tedders, Greenacres Kids Cafe in Hampton Hill and also the cafe at Krafty Kidz
Enjoy!! Fingers crossed the weathers like today