Kids Week in the West End – that grammatically suspect three weeks of free theatre tickets for children – commences on Wednesday, and to celebrate the Society of London Theatre is throwing a big old free party on the Southbank. Be serenaded by the casts of 'Billy Elliot', 'Mamma Mia!' and 'Million Dollar Quartet'. There'll also be a raft of activities including a taster session with English National Ballet, the chance to learn a 'Mamma Mia!' dance routine and the magic of 'tiger aerobics' with the cast of 'The Tiger Who Came to Tea'. There's also be juggling from The Flying Karamazov Brothers and magic from David Wood. Hosting proceedings is anguished lefty comic turned avuncular 'Railway Children' station conductor Marcus Brigstocke.