London things to do for an 8 year old

[Giraffemonkey8]

Our son loves London. We are taking him on a surprise trip soon and have already done all the obvious attractions so don’t want to do them again. Please let me know the weird and wonderful things which would appeal to an 8 year old that I might not have heard of!

Things we have done/not interested in:
Tower of London
Museums
Art Galleries
River cruise
London Eye
Palace
Covent Garden
Bus Tour
Chinatown
Harrods
Hamleys
F&M
Lego store etc
Leicester Square
Madam Tussauds

OMG, did not realise that. We didn't go that long ago! I just love the Barbican and we kind of found it by accident, it was a real gem.

The Golden Hinde
St Paul’s - right up to the top of the dome
Forbidden Planet Megastore

Paddington Experience
Imperial War Museum (I know you said no museums…)

How about trying to fit in a picnic - most of the child friendly restaurants are overpriced and really not that great. But with a picnic you can choose your own food and go and sit somewhere nice like St James’ Park where there’s a lake and lots of ducks / tame squirrels etc. (Or there are lots of other green spaces in London you could go to.)