I can't pass without dropping in, Orcs Nest is a small independent boardgame, D&D etc store that's been around forever(1987)... and has the best logo. Good selection of games for younger kids too.
Epping Forest is a 2,400 hectares area of ancient woodland between Epping in the north and Wanstead in the south, straddling the border between Greater London and Essex. I tend to get off at Loughton Tube Station (Central Line), which is about 10–12min walk to the forest.
Beautiful museum with permanent collections on anthropology, natural history and musical instruments. Surrounded by a park with farm animals and beautiful views of London skyline.
Need some clean air or just a time-out? Kew Gardens is a short train ride away from the city centre but is provides you with space, greenery and and a small holiday for the lungs. The garden contain tropical glasshouses and interesting architecture, so it is a treat for both body and mind.