I recommend the Polka Theatre in Wimbledon, London. This theatre only does shows for children. I can still remember the excitement of school trips there. Coming from a family that did not do things like go the the theatre, it opened up a new world to me.
Polka Theatre, 240 The Broadway, Wimbledon
London, SW19 1SB
www.polkatheatre.com
Google map: tinyurl.com/yfltmyv